Dear Tony,
This is a powerful painting and a poetic visual treat. I'm expecting it's another winner for you. Just as you've expressed a clear opinion about your subject in your introduction above, you are expressing a strong opinion in your paint as well. That is the hallmark of a great painting and painter.
You so poetically invent and use the light. This is not merely realism or impressionism in operation, but something more, an ideation in the poetics of opined illumination. For example, the way you mass the light on the face, yet less so on his hands, is part of a visual idealization and humanization. I expect the light falling on your subject was more even-handed and boring in reality, but here you have made an image dramatic, interesting, and narrative of this man's character. Bravo.
Garth