Sorry to bump the thread, but here's what I really want to say about this.
The first part, meaning the main melody part before the calm section, is constantly, suddenly changing, making them extremely chaotic. The brasses' over-the-top chords seems to be overdone, and some of them really seem to disrupt the flow. The transition starting around 1:30 was a little better, but the chord which has F# as the bass note didn't seem to connect properly.
I really like the second part, meaning the "calm part". I'm just not sure where's the best place to put that section, because in my opinion, it's placed too early. If I want to be descriptive, the listeners enjoy the first section, but eventually they may wonder why that section ended too short and now they're listening to the long, soothing part all of a sudden. Also, since this section is very long compared to the first section, it really is a good idea to bring back the theme from the first section to not let the listeners lose it.
I'm glad you finally brought the theme back around 3:55. Once again, make sure that your ballad part connects with the rest of the parts, to not let the listeners lose the feeling of the whole tune.
I know the original orchestral tune just enough, and what Mozart really accomplished is he carefully utilized the motif over the whole tune. I'm pretty sure catchiness wasn't the big concept when you were making this, but it is SUPER IMPORTANT to let the tune flow in a fair direction.