I know what it's like to write mostly minor pieces... that was me for a while, haha.
The dissonances you introduce in the first part are quite beautiful, I just wished more of them resolved, because after holding them a bit, they sound awkward.
The second Allegro section I was wondering where the percussion went... that took away a lot of the driving force, and more importantly, the suspense of out of it. I felt like a high point and low part could really increase the emotions in here. Also, maybe a few more deviations from the tonic chord?
It carried itself very well in the beginning, and unfortunately my expectations were a little bit let down in the second. For a first in major piece I think you knew what you were doing... just fool around with instrumentation a bit more.
Cheers!