re: WWII history buffs - Pacific theater island hopping

I'll assume your figure of ten fighter escort missions originating from Iwo Jima is accurate. But I don't think its intellectually honest to just divide the USMC and USN causulties on Iwo Jima by ten in an attempt to prove the invasion was unjustified or unnecessary.

There were other factors involved...
The primary long range escort fighter, the P-51, had a rudimentary navigation system which proved unsuitable for long over water missions, and, unlike the B-29, did not have a pressurized cabin. Pilot fatigue/discomfort was a major issue. Someone should have recognized this shortcoming beforehand, but they either didn't, or ignored the obvious.
Probably more relevant, was the change in bombing strategy. The B-29 was designed as a high altitude daylight bomber. Curtis LeMay, being the innovator and demented bastard he was, started using his bombers in low level (5,000') night time firebombing raids. I believe he incinerated about 250,000 Japanese in Tokyo one night in late March. At that point, Iwo Jima had probably been secured for about a week, maybe two.
Also, with flying time cut in half from the bases in the Marianas (Tinian, Saipan), it seems logical that maintenance issues would decrease and unit operational readiness would be increased.