This is already late as you said, you may want to just present it as a "here's a present, happy day!" gift instead of a specific event gift that would give you time to do a few more studies. I think you need to work on 'seeing' and translating 3d information into a 2d image: his back is not in perspective to itself, the centerline seems smushed in because of this.
I did a paintover of how I would approach it (I'm not great at men though, so it's mainly based off of a variety of muscle refs xD). (warning, backside) [link] I enjoyed the exercise, I may have gotten a little carried away, but how muscley he appears will basically depend on how much fat and skin you decide to drape on the form.
Ohh Thank you so much! This helps loads c: And yeah it is pretty late xD Granted I have been working on this piece for about a month and a half if not longer xD doing all kinds of studies both on the computer and human reference xD ( i feel bad for my friends sometimes, they always end up being a test monkey x3 ) And yeah with the center line, It really was just a draft with color XD I was always messing around with it.
ahaha xD I just get frustrated when I cant get it to all look right c: but this is something I do wanna get done xD I feel like it would be a piece that would have some giggles c: so that is the driving force that makes me pursue it.