You can insert it into the meat, read it and remove it to test for doneness. Charcoal and wood are interchangeable. That presumes that you understand that you don't cook over wood until it has been reduced to coals. Depends upon the meat cuts. Beef and pork will average about 42lbs per cubic foot, poultry about 35.
Bones are less dense.
Chickens and ribs would require more volumn than roasts or briskets. But a major consideration is the fire pit capacity and the ability to readily replenish the coals. Unless you intend to cook that much rather often, I'd build three 55 gal drum cookers rather than trying to make 1 big enough to do the job. Let me know how it turns out.