This seems to overstate the “legitimate doubt and skepticism” regarding the the clarity of the suttas on this issue. In short, this view seems overly skeptical.
My interpretation to this “contradiction,” as you claim, is that it is only an apparent contradiction, not an actual one. Thus, it is not a legitimate grounds for taking the suttas with a grain of salt - i.e. there doesn’t seem to be any actual basis for valid disbelief in the suttas at least in this case, imo.
The way out of this apparent dilemma conceptually seems to be to take the Dhamma-Vinaya as a whole when considering questions like this.
If one casts extreme doubt over minor apparent discrepancies, it seems like one would go contrary to the Dhamma-Vinaya, especially as stated in one or more discourses where nit-picking and fault-finding in the Dhamma-Vinaya is criticized.
It seems less likely that “there is an actual contradiction in the suttas” and more likely that the Dhamma-Vinaya as a whole must be used as a reference to address and solve any single issue.
While I think the basis for doubt and skepticism towards the topic of “karma as stated in the suttas” was grossly overstated (“we know next to nothing”), I am in complete agreement with you that a conceptual understanding is not as valuable, let alone the same as, developing the mental understanding and skill of observing the law of kamma and phala (actions and fruits) operate in one’s own direct experience.
I think even if one were to be able to do this - like the Buddha who taught the content of the suttas was - one would find themselves in agreement with the suttas, not conclude something about kamma that was not already said in the suttas.
I think that this seems to answer the question satisfactorily.
The most repeatedly definitive condition stated for not falling into states of woe seems to be attainment of first stage of Nibbāna (sotāpatti pala).
All other references to not falling into any states of woe seems to imply the “attainment of first stage of Nibbāna (sotāpatti pala).”
this might be referring to the degree of faith and love for the Buddha that is necessary for or that naturally accompanies the “attainment of first stage of Nibbāna (sotāpatti pala).”
The key seems to be referencing the Dhamma-Vinaya as a whole and using the whole thing as a context - DV features such as repetition (something said once versus ten times versus hundred times) could provide a clue regarding which principle is more fundamental (likely, the more repetitions, the more fundamental) and which simply naturally or subsequently accompany the more fundamental principles.
This seems to be my current understanding of both kamma-phala and the method by which to address other similar apparent discrepancies (by means of referencing the Dhamma-Vinaya as a whole to use contextual clues and gather evidence to come to a definitive conclusion regarding the Buddha’s view on a particular issue to whatever degree it would be possible to do that).