This will be a very high contrast lighting environment. Super bright flames, dark irons, etc.
Take an incident reading near his face with the fire up high to at least get a solid exposure there. You may want to bring a 500W shop light just to bounce a little light into the shadows.
I would also suggest a compensating developer like Diafine to help keep that contrast in check. Or, just give it a good healthy exposure and under develop the roll about 20%.