Hello Venerable! 
”Ultimately”, would only really work thanks to Dependent Origination and where it leads.
For instance:
There are partial-eternalists mentioned in DN 1.
Some of these might take one plane of existence as permanent while they view other planes or aspects of themselves as impermanent.
While eternalists are 100% certain there is indeed a Self.
This comes from their own experiences and one can fully understand why they come to these conclusions, only The Buddha could make them truly see.
Ok, so it is the same individuality that has passed through all the various lives then? 
No wonder there are eternalists and semi-eternalists in the first place! 
This happens to be the whole crux of the issue regarding eternalists and semi-eternalists.
Doesn’t matter if you call it self or individuality.
If it the same individuailty, and this individual can access vivid memories/experiences of past lives in a completely new body and a new set of khandhas but still despite this call all those past lives ”me & mine”, and fully know that it was in fact their own past lives: how and why was these even transferred to the new khandhas?
You can’t claim it is because of kamma that one can recollect those past lives where one did evil deeds and ended up in hell, much later had an awful human rebirth and slowly but surely quit doing those deeds.
Since that kamma was extinguished and one already quit doing such things a very long time ago, how can one still remember and say ”me” and ”mine” regarding those events?
Only Dependent Origination can help here.
No matter how truthful the meditators are by these very real experiences of theirs (it is not like they are making up this stuff or imagining it) The Buddha has superior insights regarding everything in Samsara.
I’ll come back to this later in this post regarding kamma, hell and past lives.
If we just for now stick to impermanence:
Somehow The Buddha knew that planes that have billions of years of duration, are very pleasant and that anyone would experience as being permanent, actually comes to an end. And by that standard it can only be called dukkha if one truly knows and sees that there is death in such a plane and it is in fact impermanent, dukkha and lastly thanks to this not-self. No dukkha during its duration.
Then we have those that have experienced countless of lives in Kama Loka compared to the long lasting ones in Rupa/Arupa Loka:
“Herein, bhikkhus, a certain recluse or brahmin, by means of ardour, endeavour, application, diligence, and right reflection, attains to such a degree of mental concentration that with his mind thus concentrated he recollects his numerous past lives: that is, (he recollects his past lives throughout) one aeon of world-contraction and expansion, throughout two, three, four, five, or ten aeons of world-contraction and expansion. (He recalls:) ‘Then I had such a name, belonged to such a clan, had such an appearance; such was my food, such my experience of pleasure and pain, such my span of life. Passing away thence, I re-arose there. There too I had such a name, belonged to such a clan, had such an appearance; such was my food, such my experience of pleasure and pain, such my span of life. Passing away thence, I re-arose here.’ Thus he recollects his numerous past lives in their modes and their details.
“He speaks thus: ‘The self and the world are eternal, barren, steadfast as a mountain peak, standing firm like a pillar. And though these beings roam and wander (through the round of existence), pass away and re-arise, yet the self and the world remain the same just like eternity itself.
Still from DN 1 regarding eternalists but it answers your questions:
“This, bhikkhus, the Tathāgata understands. And he understands: ‘These standpoints, thus assumed and thus misapprehended, lead to such a future destination, to such a state in the world beyond.’ He understands as well what transcends this, yet even that understanding he does not misapprehend. And because he is free from misapprehension, he has realized within himself the state of perfect peace. Having understood as they really are the origin and the passing away of FEELINGS, their satisfaction, their unsatisfactoriness, and the escape from them, the Tathāgata, bhikkhus, is emancipated through non-clinging.
A non-buddhist meditator will never be convinced that eternalism is not the case and will still claim that there is a Self (they have vast experiences as if there actually is an eternal self) unless you point to Dependent Origination and ”the origin and the passing away of feelings, their satisfaction, their unsatisfactoriness, and the escape from them.”
So no matter how pleasant Rupa/Arupa Loka is (that is the reason lust for these planes of existence are among the the 5 higher fetters) one has to say to all of that and to all past lives or even future lives in Kama Loka or wherever else: ”This is not me, this is not mine” And the same has to of course be applied to the 5 aggregates of clinging.
I actually don’t see kamma as an impersonal law at all.
How could the very personal choices and deliberate actions, speech and thoughts one does has, result in something impersonal?
One can only practice to the best of their ability and benefit other beings by keeping the precepts/dana/teach dhamma. But keeping the precepts is no guarantee other beings will not kill, steal, rape or lie to one. Fools do not commit such deeds against others because of the past lives kamma that person happens to have. They do it based on their own kamma.
I do agree that certain deeds can put one in certain unfavourable circumstances in the human realm:
”And suppose that fool, after a very long time, returned to the human realm. They’d be reborn in a low class family—a family of corpse-workers, hunters, bamboo-workers, chariot-makers, or scavengers. Such families are poor, with little to eat or drink, where life is tough, and food and shelter are hard to find. And they’d be ugly, unsightly, deformed, sickly—one-eyed, crippled, lame, or half-paralyzed.”
Now it turns out The Buddha in a sutta remembers a past life where he was a chariot-maker…
I don’t want to speculate what it was that maybe led him to hell prior to being a chariot-maker but I hope you get the idea that ”And suppose that fool, after a very long time, returned to the human realm…reborn in a low class family…chariot-makers…Such families are poor…little to eat or drink…ugly, unsightly, deformed, sickly—one-eyed, crippled, lame, or half-paralyzed.”
So how is it possible for the khandhas to still have access to all this or Maha Moggallana also remembering being in hell when that type of kamma is already extinguished and has been for maybe many eons?
As to the reasons why certain things happened to arahants, feel free to post from the suttas but as far as any other sources trying to explain (Commentaries, Jatakas etc.) I take all these with a grain of salt.
Kamma is too complicated to really discuss, there are other factors that come in to play that I could mention but kamma is really intertwined with rebirth and certain circumstances in that next existence.
Not so much how others will treat you or do to you, that is their kamma.
I disagree with this based on reverse dependent origination, but am really thankful that I might finally be able clarify my perspective regarding this and even regarding Nibbāna.
Here we go:
And what is a path to company with Brahmā?
Firstly, a mendicant meditates spreading a heart full of love to one direction, and to the second, and to the third, and to the fourth. In the same way above, below, across, everywhere, all around, they spread a heart full of love to the whole world—abundant, expansive, limitless, free of enmity and ill will.
This is a path to company with Brahmā.” - MN 97
Now please also take the following into account:
“At one time, mendicants, I was staying near Ukkaṭṭhā, in the Subhaga Forest at the root of a magnificent sal tree. Now at that time Baka the Brahmā had the following harmful misconception: ‘This is permanent, this is everlasting, this is eternal, this is whole, this is imperishable. For this is where there’s no being born, growing old, dying, passing away, or being reborn. And there’s no other escape beyond this.’
And this that I mentioned in my earlier post:
”The lifespan of the gods of Brahma’s Host is one eon…
…a disciple of the Buddha stays there until the lifespan of those gods is spent, then they’re extinguished in that very life.
If you take these three things together you get the following:
Spreading a heart full of love (metta) above, below, across, everywhere, all around, they spread a heart full of love to the whole world—abundant, expansive, limitless, free of enmity and ill will.
This is a path to company with Brahmā.
Baka the Brahmā had the following harmful misconception: ‘This is permanent, this is everlasting, this is eternal, this is whole, this is imperishable.
The Buddha tried to show Baka the Brahmā this was not the case in MN 49.
No other except The Buddha has pointed out that not only ”The lifespan of the gods of Brahma’s Host is one eon” but that all the planes above in both Rupa Loka and Arupa are also impermanent.
Now if we go back to the eternalists in DN 1 the Buddha says the following:
‘These standpoints, thus assumed and thus misapprehended, lead to such a future destination, to such a state in the world beyond.’ He understands as well what transcends this, yet even that understanding he does not misapprehend. And because he is free from misapprehension, he has realized within himself the state of perfect peace. Having understood as they really are the origin and the passing away of feelings, their satisfaction, their unsatisfactoriness, and the escape from them, the Tathāgata, bhikkhus, is emancipated through non-clinging.
Having understood as they really are the origin and the passing away of feelings, their satisfaction, their unsatisfactoriness, and the escape from them, the Tathāgata, bhikkhus, is emancipated through non-clinging.
This quote above shows that these standpoints regarding eternalism, thus assumed and thus misapprehended has to do with feelings and nibbāna is that attainment where the one who enters it does not feel anything at all.
You know very well from all our various discussions that I reject ”mere cessation” that you and others adhere to.
But maybe the following will make you see that I am certainly not an eternalist by any stretch for rejecting
”mere cessation” nor have I ever claimed
that Nibbāna is ”something”.
“If you say that ‘when the six fields of contact have faded away and ceased with nothing left over, something else exists’ you’re proliferating the unproliferated.
I have only pointed out that the following from the suttas:
“Could it be, sir, that a mendicant might gain a state of immersion like this? They wouldn’t perceive earth in earth, water in water, fire in fire, or air in air. And they wouldn’t perceive the dimension of infinite space in the dimension of infinite space, the dimension of infinite consciousness in the dimension of infinite consciousness, the dimension of nothingness in the dimension of nothingness, or the dimension of neither perception nor non-perception in the dimension of neither perception nor non-perception. And they wouldn’t perceive this world in this world, or the other world in the other world.
And yet they would still perceive.” <————
So both The Buddha (AN 10.6) and Sariputta (AN 10.7) affirm that in a state of immersion beyond all the planes of existence, which happens to be such an attainment where the one who enters it does not feel anything at all:
One can still perceive.
It also happens to be that this attainment beyond existence is light:
“Where water and earth,
fire and air find no footing:
there no star does shine,
nor does the sun shed its light;
there the moon glows not,
yet no darkness is found. <—————
It also happens that the disciples in higher training in MN 1 are told not to delight in Nibbāna.
He directly knows extinguishment as extinguishment. Having directly known extinguishment as extinguishment, he does not conceive it to be extinguishment, he does not conceive it in extinguishment, he does not conceive it as extinguishment, he does not conceive that ‘extinguishment is mine’, he does not take pleasure in extinguishment. Why is that?
Because he has understood that taking pleasure is the root of suffering, and that rebirth comes from continued existence; whoever has come to be gets old and dies. That’s why the Realized One—with the ending, fading away, cessation, giving up, and letting go of all cravings—has awakened to the supreme perfect Awakening, I say.”
Because that is all I’ve actually pointed out in all these discussions we’ve had and it does not make me an eternalist nor someone who is proliferating the unproliferated.
Unless you claim that The Buddha and Sariputta are the ones who are actually proliferating the unproliferated; just because it is declared that in that attainment where the one who enters it does not feel anything at all, one can still perceive and there is light?
So I hope it is clear that you can never put me in the eternalist camp nor that I am somehow proliferating the unproliferated. I really hope this is clear now. 
——————————-
But on the other hand if we take the view of ”mere cessation” one is indeed proliferating the unproliferated when claiming such things as this:
“If you say that ‘when the six fields of contact have faded away and ceased with nothing left over, nothing else exists’, you’re proliferating the unproliferated.
That is mere cessation in a nutshell.
If ”mere cessation” was really true it would never be considered as proliferating the unproliferated, that ‘when the six fields of contact have faded away and ceased with nothing left over, nothing else exists’,
And claiming that there is a difference between so-called annihilationism (complete termination) and ”mere cessationists” since mere cessationists claim there is no self, while annihilationists imagine there is a self that is being annihilated, is just a play with words.
There is not a single difference.
Now at that time one of the monks had the thought,
“How do you know and see in order to end the defilements in the present life?”
Then the Buddha, knowing that monk’s train of thought, addressed the mendicants:
“Mendicants,
I’ve taught the Dhamma analytically.
I’ve analytically taught the four kinds of mindfulness meditation
the four right efforts,
the four bases of psychic power,
the five faculties,
the five powers,
the seven awakening factors,
and the noble eightfold path.
That’s how I’ve taught the Dhamma analytically. Though I’ve taught the Dhamma analytically, still a certain mendicant present here has this thought:
‘How do you know and see in order to end the defilements in the present life?’
Perhaps they don’t regard form or feeling or perception or choices or consciousness as self. Nor do they have such a view: ‘The self and the cosmos are one and the same. After passing away I will be permanent, everlasting, eternal, and imperishable.’
Remember, this is a sutta about how to know and see in order to end the defilements in the present life (Nibbāna).
The Buddha mentions prior to teaching, the many ways he has taught the Dhamma:
“Mendicants,
-
I’ve taught the Dhamma analytically.
-
I’ve analytically taught the four kinds of mindfulness meditation
-
the four right efforts,
-
the four bases of psychic power,
-
the five faculties,
-
the five powers,
-
the seven awakening factors,
-
and the noble eightfold path.
It is only The Buddha that teaches not to regard the khandhas as self and those in the sutta already adhere to it, so they are obviously buddhists.
These same buddhists reject: ‘The self and the cosmos are one and the same. After passing away I will be permanent, everlasting, eternal, and imperishable.’
Once again this is actually buddhist ”mere cessationists” in a nutshell.
No difference whatsoever.
So please forgive me when I get called an eternalist or someone who proliferates the unproliferated when it ought to be clear I’m not,
that I in return see ”mere cessationists” as 100% proliferating the unproliferated and for pointing out that there is no difference at all between the buddhist-”cessationists” who reject eternalism and their views regarding ”how to know and see in order to end the defilements in the present life, which is of course Nibbāna.
What troubles me about this ”mere cessation” view is how the text in AN 4.174 has clearly been altered.
It now says if one clicks on it: AN 4.174
“Reverend, when these six fields of contact have faded away and ceased with nothing left over, does something else exist?”
“Don’t put it like that, reverend.”
“Does something else no longer exist?”
“Don’t put it like that, reverend.”
“Does something else both still exist and no longer exist?”
“Don’t put it like that, reverend.”
“Does something else neither still exist nor no longer exist?”
“Don’t put it like that, reverend.”
It used to look like this, only a few weeks ago:
This first translation in this screenshot above was correct and coherent with the:, ”nothing else exists”.
But that would show that ”mere cessation” is actually proliferating the unproliferated and so it has instead been replaced with:
“Does something else no longer exist?”