I'll go through movement by movement.
Movement 1: It was an enjoyable movement, but I noticed a few things. The opening fugue had an interesting subject and I think you harmonised it quite well, but it felt like for the other voices you wrote a measure, copied and pasted, and adjusted the notes. It's not necessarily wrong, but it does sound uninspired, and I think you could do much better. One part in the subject also reminded me of Liszt's Hungarian Rhapsody no. 2 . In other places throughout this movement some voices lose their independence by following another line in parallel thirds for too long. Also not necessarily wrong, but it does make it sound like 3 voices instead of 4. Another thing I noticed is, though it is in sonata form, I couldn't really pick out the themes. Might just need another listen, but I think it's a sign they don't contrast enough. This might also be caused by the monotony of the string samples. I also found the recitative part to be a bit random and disconnected. Maybe have more parts like that or just completely remove it? Besides these, the only issue I have are the weird rests, like what Quinn pointed out.
Movement 2: This one was great fun. It had a real sense of motion and energy, something that I struggle emulating. One issue though, is that the enharmonic spelling was chaotic and there were rest issues like in the first movement. I won't point out specific instances since it's probably just from a lack of polish. Just be sure to go through all that. I also noticed the movement ends abruptly. Must not have written a coda?
Movement 3: I liked the material in this one. I agree that the counterpoint could have been better. There were moments where it was more homophony than polyphony and other places where it was a little dissonant. I noticed some passages toward the end that have slurs which stretch over a bit of a long distance, and many of these notes were the same in succession, which defeats the purpose of the slur since you can't really do that in one bowing, you'd have to lift up. Examples measure 138 and 156. I also found the lengthy pauses in the middle and at the end to be unnecessary. Maybe they were supposed to be filled out later, but you didn't get to it? Can't tell.
Movement 4: I liked that the middle movement was brief honestly. It helps give the sense of a midpoint. I think that marking those sections as recitative is unnecessary though, unless you're asking the string players to play it a specific way. I also think that the section starting on bar 19 was a bit abrupt and could use a smoother transition, unless your goal was for it to be abrupt.
Movement 5: I thought this one could have been a bit longer. If you make this movement around 10 minutes or so, that will give the piece a nice symmetry.
Movement 6: I honestly liked this one alot. Its more upbeat mood provided a great contrast to the rest of the piece. And though the variations weren't as "varied" as they could have been, I still think the movement holds up. On top of that, the melody was quite beautiful. However, I noticed that EVERY SINGLE NOTE of this movement has a tenuto mark. You may know now, but I'll explain anyway just in case. For string instruments, a tenuto instructs the players the use a fuller bowing. In other words, use more of the bow. If you want the whole movement to do this, that's perfectly fine. It would just be better to write at the start of each instrument "sempre tenuto", or something along those lines, instead of putting the tenuto mark on every note. Another thing is that you have tenuto marks on pizzicato. You can see how plucking with a fuller bowing doesn't make any sense. This movement also suffers from the weird rests problem. Other than that, this is probably my favourite movement thus far.
Movement 7: I was a little disappointed that there was a pause on the mp3 since this was clearly supposed to continue directly from the previous movement. Oh well. I really enjoyed parts of it, especially the more dramatic section. I personally thought the section starting on measure 155 was a little repetitive and it honestly kind of bored me. I personally didn't really like the melody either, but that's just my opinion. I thought this movement suffered from a lack of strict structure, and I agree with you that the sections weren't glued together very well. Maybe rondo form would work nice? Or maybe sonata form? I don't know, but either way, reorganising the sections I think would benefit. I also noticed at the end that you briefly brought back some material from the start, which is always cool, but the ending itself didn't really satisfy me. This movement also suffers from weird rests syndrome.
Overall, I think the piece has great potential, it just needs a lot of work. From seeing some of your other compositions, I think you are completely capable of turning this piece into an absolute banger 👍. Thanks for sharing.