Tony didn't have the time to think about the minutia of what he could with whichever stone in the heat of the moment. He had one opportunity to turn the tables as emphasized by Dr. Strange. He seized that moment and did the simplest thing he could do before Thanos could react and retake the Gauntlet.
That's a fair point. But Thanos didn't seem too badly harmed during his first snap--where he wished away so many.
The second snap--where he used the stones to destroy the stones--that I can see as having cooked him.
Now--what happens to the glove?
In the comics, Adam Warlock gets it, but he was only hinted at in the last Guardians of the Galaxy film.