If he can dig himself out of a grave that he was buried alive in with the jaw of his decomposing partner in a week, and still live, he can survive being shot in the chest, and burnt.
In that chapter ghost said “why do we have to wear these fireproof vest”
Well if you watch Ghosts “death” in MW2…he didnt actualy get burned! He was shot in the shoulder (plus these people wear bullet proof and fire resistant vests) and the
petrol was poured all over Roach,none went on Ghost. So the S.A.S sniper team at the start of the level could of easily saved him.