The US occupation of Iwo Jima saved the lives of many US fliers whose battle-damaged planes had to land there while returning from combat over Japan.
Not sure that is true.
First most B-29 aircraft that landed there did so on “training” missions.
Second, even aircraft that may have ditched about that far from Japan might have parachuted out and been picked up by the Navy.
Certainly the airfields there were useless to the Japanese, as they had no meaningful amount of fuel. It is open to question as to how sure the various commanders may have been of that aspect of Japanese want.