Scott
Obviously, if the coals died when the top was closed, then heated up again when it was opened, there wasn't enough oxygen. You didn't mention where the vents were, or how many. If they were all along the bottom, or the top, they don't do very much. You need vents both top and bottom to get airflow through the coals. And you need enough area to give sufficient flow. Again, obviously, some of these conditions are not being met when the top is closed. In his grilling cookbooks, Schlessinger recommends leaving the top open for all grilling. The only time he recommends closing the top is for slow cooking, like true barbequing. I'd highy recommend you get "Thrill of the Grill" or "Licensed to Grill" and read the introductory material. Some of his ideas are controversial, but on the issues we're talking about here, I think it would help. Otherwise, leave the top open! With a properly designed grill, you should be having the opposite problem - having more heat than you need, which is much easier to deal with.
As for holding your hand a given distance from the grill to test for heat level, I've always believed this is ridiculous. The range of tolerance between individuals for heat on their extremities is huge! People who work around furnaces all day could quite comfortably hold their hand almost indefinitely where others would pull back in seconds. Even if you don't work around heat, your tolerance, like general pain tolerance, can be several times that of another person. I think a thermometer or some other more objective measurement is more meaningful.
Suggestions 2193cathyxyz Okay, have a bowl of potato-leek soup in bread bowls and eat the bowls. The soup: 2 large white potatoes, peeled and diced 2 large...