I don't think we're too far apart here.
I don't think bombing civilian centers in Germany, Japan, or Britain (leaving aside the atomic bombs) shortened the war by one day. So ultimately LeMay's contributions were pretty marginal. However, that's hindsight, so I wouldn't argue that either side was wrong to try.
As for the Soviets, I personally would have been quite worried, seeing what they had done to the Nazis. The Japanese army had what, a million soldiers in China? Who's to say Stalin wouldn't have wanted to take China too? If we hadn't opened a second front, I think he would have marched all the way to the Atlantic and turned Western Europe into satellite states as well.
We are agreed about the evil of the Japanese military. They murdered millions of civilians, tortured POWs, and had contempt for everyone, including their own civilians.
I'm not going to say anything bad about Tibbets. Like I said, if I were Truman I would have done the same thing. But if people vote for Tibbets, it's to celebrate Hiroshima, which shouldn't be celebrated.
Both of my grandfathers fought against the Nazis. No idea if they would have been transferred to the Pacific, but we shouldn't have risked one more person to defeat Japan than we absolutely had to. I'm glad your grandfather didn't have to go.