Lots of good stuff here.
First, I'm extremely impressed. Shooting a guy AND not shooting boudoir...that's a huge change in style and genre for you and yet you produced some great initial work. Each photo has some stuff I'd want to change. But basically, for the change in what you were shooting AND the intention of the shoot, you got good results.
My take...
#1: Very effective, very stark, some extreme dynamic range--which I think works for the nature of the shoot. Forehead is blown-out and you should correct that. I'd like to see a little more of his left eye too. But otherwise, quite good IMHO.
#2: Very good. Which his hair didn't blend in to the background--some backlighting might have helped with that. You can work on it with post production. And while I like the portrait orientation with the two background lights of a warm color, I think you should take a look at a landscape orientation with no lights (they're cut out by going to landscape). Given his seating/pose, that may be more effective for him.
#3: Very effective except for the heavy deep shadow on the wall from his head-hair. It makes him look like he's got a HUGE head. That's a big drawback for me visually. Anything you can do to lighten that shadow would be a big plus in my mind. Otherwise, I love it.
#4: It's okay--out of all the shots you shared, this is the one I'm the least excited about. Not bad, just doesn't reach out and grab me like the others do. His hips look big in this pose so it takes away from the vertical flow. Lots of clutter in this shot (the white trash or plaster at the bottom of the fire escape for instance). I'd edit out that window in the far upper right--it's distracting in my opinion. And the vertical lines are distracting to me...I found myself looking at them to see which ones were straight and which ones at an angle. In theory this should be a very effective shot. In execution, it was just "meh" for me...not bad but the weakest out of a very powerful set that you have. I think this is a good setting but it would work better with a different pose (where he isn't facing the camera straight on) and maybe a grittier form of dress (think of him in jeans and a T-shirt, and light the background a bit more so you don't have a piece or there jumping out to distract but instead the backdrop is the setting.
#5: very different look when compared to the others. Love the highlights in his hair. I'd eliminate his right earlobe--that highlight/little glob of white doesn't enhance the photo in my opinion. I'm torn...part of me likes the straight vertical lines of the jacket open on his chest. And part of me wonders what it would be like if the bottom of the jacket had been closed so we saw the makings of a "V" from that jacket, adding some diagonal lines. I think you've got a lovely shot here and I'm just speculating what tweak might have made it more powerful. Maybe if we saw more of his torso, the "V" effect would work better. As is, you may have made the right choice.
Overall, good set...especially considering that it's not just a guy but unlike narrow DoF, soft, hazy, romantic boudoir themes, this is almost the complete opposite...nothing soft and warm and cuddly about this feel, instead you're looking for a stronger, more dynamic feel and you got it with these shots.