OP nicely written. Let's also not forget he has not missed many games so he has played many more games/snaps than others in the last 5 years. Also some of the worst INT guys suck and simply don't play that long and get benched.
I'm too tired to look it up but Josh has fumbled the ball a ton as well. Again he has more dropbacks and carries than probably any other QB during that time. But still numerically he is turning the ball over quite a bit. He cleaned up the fumbling quite a bit but it still has hurt him from time to time like Minn last year, Dolphins playoff game, and Jets this year.