A5s nut flush river over bet all in board pair, hero call/fold?

That classic family pot ahahah
Turn is more than fine.
He can have 88, 77, 66 maybe even KK. But you have a monster.
Very very tough spot but I'm going broke here too.
Im also playing some zoom and the advice I can give to you is to play tighter than normal when you have no info.
Coolers are the everyday fare.
I really don't know why variance is bigger on zoom. The game is the same you just play more hands, which in fact contributes to reduce variance.
Coolers and variance are different things.

Maybe he push K high flush draw or lower and some 7x hands, AA and AK.
No i know what is cooler and variance but i read lots for zoom, and the most of people write bigger variance zoom than regular tables. But only one thing what is very important and you wrote, here play more tighter. I prefer regular table than zoom.

we're in position, so i'd actually be very inclined to stab the flop and take it from there. we have a strong draw that can cooler villains and it's also the "nut air", i don't mind considering firing two and checking behind the river when we miss. facing a check/raise would not be ideal, but we can continue there too.

as played, i believe that river is somewhere between 0 and slightly negative EV. i love how villain played it actually

I would bet on flop too when all other players check.

Yes you right, standard move post flop bet, when other players check, in the positon. Most of time i bet, but zoom not is my favorite game. This was my mistake set down in zoom.

Maybe a bet post flop would be the best choice, but It's easy to tell after SD. I would probabily do the same on River.

I wouldn't limp preflop. I would raise or fold.
On the flop, when being checked to, I'd take a stab at it. We might pick it up with Ahi which is nice, when called we create a bigger pot for when we hit the nuts. We aren't obliged to fold either when we get c/r'd (depends on sizing).
As played I think the river is a close fold. Your hand is somewhat face up and he expects to get called all the time here. Also, it's NL2 zoom and ppl never bluff rivers here.