Hi, thanks for the advice on the modulation. I was clearly overthinking that part to the point of confusing myself. I should have taken a step back and just reworked those few measures without trying to force adherence to the harmonic structure of the previous, similar sections.
The idea with the piece ending at a higher tempo is that the parts would loop independently - the beginning would loop until time begins to run out, which causes the modulation and speed up section to play, followed by the urgent, higher speed part. So there is no intent to loop the earlier sections, because we want to keep up the pressure without reintroducing the more relaxing accordion or some slower feeling parts dominated by longer harmonies.
Again, thanks for the constructive criticism, I'll definitely spend more time actually learning about proper modulation technique.