Upload & Sell: Off
I have a hard time following it all. Maybe a short summary would help.
On the photos, the first one looks best. The last one is in my opinion not as great.
To separate the black suit from the background, why not pull him further away from the background and use grids, etc. to focus the light on him and not the background (I assume you did use grids). From there, just adjust the light such that highlights are not blown, and get the fill ratios you like with modeling lights or experimentation. The background would be relatively black, even with a fair degree of fill due to inverse square law.
So far as I know, the main sensor limitation is blown highlights. Sure, some have more bit depth and therefore more levels of gray, etc., but the universal limitation is blown highlights. Max out the highlights to be just sub clipping, and the world is your oyster. From that point, you can manage the file best, blacks included. Curves might be the best way to do it, though lightroom can basically do curves with sliders now.
The problem with dodging and burning in this situation is that without masking, which would be problematic here, you will be spilling over into the background with your brushing.
To me, the last photo looks washed out somewhat (not as much as the one before it, but more so than the first one).