1. Floyd is going to stop Cotto. IMO, between rounds 6-8.

2. Stamina shouldn't even be a question. Floyd knows how to slow a fight down. No matter which Cotto comes out, Floyd's ability to adjust to any style, can slow a fight down. If Cotto try to fire 3 or 4 punch combinations, Floyd can laser tag him. If Cotto attack the body, Floyd will get in close and smother Cotto's punches and fight in the pocket. If Cotto try to counterpunch, Floyd will stomach jab him until he's zapped.

BUT
3. Floyd's chin? Floyd is getting older that's one. 2. He has been rocked a couple of times. Shane most recently, Chop Chop and Judah. He just recovered so quickly and was able to dominate seconds after we tend to forget. Hatton even had Floyd off balance. So I'm still of the opinion that Floyd's chin just haven't been tested enough to say its great.
Saying that . . .
Cotto best chance of winning to throw while Floyd is throwing and try to catch Floyd in an exchange. Difficult, I know cause Floyd will only throw one punch and look for Cotto's best punch coming back. Or Cotto can play possum. The one flaw I see Floyd having is when he tries I finish his opponent, he square his stance up. Besides that Floyd by KO 6-8.