Hey--
First, congrats on your musical staying power!
I listened to the first movement. And finished it. For me this is a compliment as I have little time and I usually can't get that far...
I think a comment by Omicron sums up my general feeling of the movement:
I notice many modulations and ideas coming in and out. Though some are based on the main motive, one could get lost on a first listening. Not that this is necessarily bad, but I feel that the section that begins with the above measures could work alone as a movement itself.
I recall from reading when Felix Mendelssohn's father brought a sample of 15 year old Felix's compositions (the piano quartets if I recall correctly) to Cherubini, asking him what he thought-
His criticism: Too many ideas in each movement!
Focus, develop.
Other than that, he recognized a first order genius who would do well. he was right.
And so my impression, as an informed listener, is that this movement suffers from to many ideas. While I am convinced you can harmonize anything, and write counterpoint for anything, the real question for any composition is WHY? ( WHY all the modulations? (for example). If things are getting stale, reiteration in another key will only go so far...)
As Omicron suggests, focusing on 3 or 4 ideas, developing with an ear towards HOW IT FEELS as a listener would bear immediate fruit.
Lead with the heart, not the head.
I see you have many philosophical ideas (as did Mahler, interestingly), but music --as any film score composer knows-- is, ULTIMATELY about the FEELS.
That is why John Williams is a multi millionaire and _______________ (fill in any academic or late 20th, early 21st century composer) are at best "doing well".
Your technical competency is excellent. I would do less to do more.