I would fold ATo on the sb to a raise (depending on villain), but I prefer 3bet to call. And flop is most definitely a fold when he raises. Yes, sometimes he has a flush draw and we fold the better hand, but usually it's a better ace and we're crushed. 3bet pre is ok if this guy is raising a lot of hands in late position. And if he 4bets us, AT is such an easy lay down. But I prefer to fold, I'm just not interested in raised pots oop with AT, it's a weak hand. I'd sooner play 67s anyday.

All in on river is bad, his calling range to a shove includes no hands we beat. Shoving this river would be a bluff, it's very important to know when your bet is a bluff or a value bet. There are 0 hands that we beat that he can call, so there is no value. There are some hands that can fold that we lose to, such as AJ for example, so there is bluffing value, but not a lot. This is not a great spot for big pot action, pick your spots better.