Hey man - wow, that's dedication
I've seen your studies, they're great, but you still need to apply most of them to the work you're doing. What I'd suggest is to go slower, and really look at things and measure carefully.
The first hand in your last update for example, is good, but the second one's proportions are off.
Looks like you've had a peek at Nicolaides' book. Glad to see you posting. Biggest crit - watch your forms. Internal detail's great, but great detail on form that's not quite there is a bit funky. It's kind of like having a beautifully rendered face on top of a skeletal structure that doesn't make sense. Example - the gun in post 216. The form looks off even tho the detail looks accurate.
Also think your sketches would benefit greatly by slowing down some. It looks like everything's pushed out really, really fast. While speed has its perks, seeing without thinking about what you're seeing can also create some really, really bad habits (and they're damned hard to break...). As an example: In terms of drawing figures, since I see that you're doing studies, you do slow, thoughtful studies so you know the forms, the way things work. You've got the knowledge of what goes where. It means when you do a speed drawing from life or from imagination, the knowledge that's in your head fills in the gaps between what you're seeing and what you're drawing.
So that is my advice to you. Keep up the work. And take some time, slow down.
If that gets boring, I've found a really fun practice exercise is taking classical compositions and replicating them but with stick figures. The key to this is to really focus on composition and how figures/objects/lines relate. I'll try to post a tutorial on this in the next couple of weeks. I'd recommend most of the Italian Renaissance painters. I'm partial to Titian But most of them will do. Brilliant comps.