Few complaints here, although I'm probably the least qualified to comment on musical form. There were a couple of passages that gave me pause. The 2nd beat of m35 includes an 8ve in the 1st and 2nd voice... I wonder if that might be destabilized with a 5th or 6th instead (which would also match the imitative leap in the 2nd voice at m37)? Also, the harmonic progression to the end of the first phrase (m40) isn't quite convincing to me. We do make the transition to the dominant by m36, and this is maintained through m38, but then there is a lowering of the dominant's leading tone back to B-flat. Would that be strengthened, I wonder, if the leading tone to the dominant were continued to be raised (which might also necessitate a change in the bass notes in m38)? Likewise, the progression at mm42-43 isn't quite convincing, perhaps because the initial chord at m43 is a bit ambiguous. (Is it a species of C chord? Amin7? Em?)
Really, though, it's a fine piece. As far as I can tell, you have a solid grasp of voice leading and counterpoint. And it's your music, so you can do with it what you will. These are simply my preferences and should only be taken into consideration if you agree with them!