$1.50 6max hyper ATs

I think your thought process is pretty accurate. The call is on the edge. I think the openshove is a TP maybe even 2nd pair. Sets he would just c-bet to get more value. I believe his shove with such cards is pretty good because of the huge pot in the middle and the cards aren't hitting the calling ranges hard.

If it were a bet and not a shove, I could have shoved my stack into his bet, possibly (since villain is total unknown) making him fold his 2nd pair or weak draws kind of hands. I would have liked that line better than the one I posted here. Thoughts on that?

A bet like 1/2 to 3/4 potsize on a 4-way flop looks super strong, so with a shove over a such a bet you're only way out is to hit that flush so 9 outs.

Good call. Most of time we have flush outs and top pair outs versus his shove. Even if he has like K7 we have over 50% equity. From cEV we need 41.2%. With ICM tax it does go up to something like 44-45%. With two overs and nut flush draw we get that always versus his range. Especially when villain rarely shove most premium hands in this spot.

If someone calls from behind it will basically just get us more value.