Hi @Bethl. Good work on delving into the meaning of these verses through the Pāli. If I’m reading what you wrote correctly, then you seem to have turned around what I did say and what the verses actually say.
When the first two verses say sabbe saṅkhāra aniccā and sabbe saṅkhāra dukkhā, the implication is that all things conditioned are impermanent and suffering, but saṅkhāra excludes nibbāna (which is unconditioned). And then the 3rd verse tells us that absolutely everything (sabbe dhammā), both conditioned and unconditioned, so even including nibbāna is anattā (not self).
Is that clearer now?
As to the 3rd line of each verse, yes, here dukkhe is locative singular and I would translate nibbindati as “becomes disenchanted”, pretty much the same as Bhante’s “grows disillusioned”.