How much can it kill you when you get burned by fire (even in the face)?

Well...once you've been killed, it's pretty much 100%. On a more serious side, it doesn't even require direct contact to flame to kill you. A lot of fire deaths occur when the respiratory tract becomes burned, usually due to breathing in hot ges, and swells, cutting off air flow. If you want real experiences with firefighting, I would NOT suggest Backdraft. Go with Ladder 49 or Fireproof.