So, I looked over the piece for a couple of hours and listened to it a few times and this is what I came up with.
It is is Sonata form, although not so clear.
I believe that mm. 1- 24 is an introduction, in Bb major. The exposition and Theme 1 then starts in the key of F major, this lasts from 24 to 53. Although it modulates back to Bb around mm. 31. From 53-70 there is a transition to Theme 2 and is modulating to Gb major. Theme 2 begins in mm. 71 with the key change to Gb and lasts until the repeat.
The development begins in 94 and modulates into the key change to D major. The development is fairly short, going through another key change to G major (and possibly modulating briefly to C major), before recaping at 132.
I then believe the recapitulation starts in 132 with Theme 1' back in the key of Bb major and modulating to Eb major around 139. Theme 1' then goes until 160, where the transition into Theme 2' starts. It also modulates to Ab major in 150 leading the way to the key change. This transition is longer than the one in the Exposition, but it reaches Theme 2' in mm. 189. The key makes it's way back to Bb with another key change at 173.
The movement then ends with a Coda starting in mm. 214 in Bb major.
I also did analysis of the key centers and I got something like this:
Bb [ F Bb Gb] D G (C) [ Bb Eb Ab Bb] Bb
V I N/V V/G vi (V/C) (ii) V I IV V I
( Eb temporary tonic)
Intro Exposition Development Recapitulation CODA
I was curious of the Gb, since it isn't a related key, but I thought it was interesting that N can subsitute for IV's. Eb also is the IV of Bb....I'm not sure what it all means in relation to the big picture, but its a start...
This maybe right or wrong, but it was the closest I could come to making sense of it in Sonata form.