Hey there,
I started an overpaint yesterday but didn't have time to finish it then. But then I took a look at your sketchbook and noticed that you've been working on this for a while. I did this overpaint before seeing that, so I didn't see the The last version of this you posted, the line art with the very good perspective in your Sketchbook. It pretty much solves all the issues I have with the piece at the moment! There's a few things to adjust with the values and the rendering, I think, in this version, but I would suggest following that line drawing you did. The composition is better, the pose feels more natural and the forms in the anatomy seem more realistically indicated
The way you've rendered your forms is a bit unnatural . Where they are is fine; your anatomy is fine and for the most part so are your proportions. However, you're rendering all these shapes extremely roundly and with very harsh edges. You might want to try condensing your values and flattening your shapes a bit If you look at real muscles, they rarely end at a sharp edge like that. Even the most ripped guys will always have a bit of a flow to the edges, and the musculature is more rhythmic than this, with a lot of accelerated round edges rather than round ball shapes
Yes they wrap around the form, but really for the most part you can follow perspective lines, albeit a bit loosely, when you start to render the muscles in value. Think of each ab, for instance, as fitting in a box. How would that box look in perspective? You can then fit the contours of that ab to that perspective. Here's a picture. In blue is the "box logic" of the muscles, loosely, and in red-orange is how the forms react to that
If this a piece you're trying to do strictly from imagination, there's no point really continuing for so long struggling with something you don't really know yet. Take a peek at some reference, analyze it but don't copy or reproduce it and then bring it into your work. In my experience you'll learn better than by struggling and getting frustrated trying to resolve it when really its just that you don't know how to do it in the first place
Hope that helps