You absolutely do not have to decide if you're stacking off when you call this flop.

A fish will extremely frequently define his range on the turn/river by betting less with air and marginal value hands that are "raising for info" etc on the flop and hammering the nuts. Making your decision for your stack before you get a ton more info on a later street is a retarded mistake unless you for some reason know he's going to bet turn and river large regardless of what he has; we have no reason at all to assume this.

Can't imagine ever folding this flop for this price since lesser pairs are easily possible as well as the odd bluff.

You get such a great price on the turn and river and he's also defined his hand as somewhat more likely to be marginal than the nuts given his shitty sizing. Folding at any point given these odds would be pretty horrible.