Call always. Villain doesn't have JJ and AA in his range so the only hand you are losing to is 55, which are only 3 combos. Obviously there are many more flush combos than 3 combos of 55. Also villain would probably c/r OTT trying to gii on this wet board with a set. You only have to be right 33% of the time on the river and you are winning way more than 33% of the time when villain plays like this.

His line is terrible with w/e.
He shouldnt have too many flushes other then JTss and that would be a pretty ambitious shove when you have all of the nut flushes in your range, but its still possible.
Dont really see what he could be bluffing with though, so id probably sigh fold as well all though i wouldn`t blame you for calling either.

I think you're only beat here by Ad8d Ah8h. 55 should be raising on the flop most of the time. If you're folding KsQs here you're only calling with 55 and that can't be correct.

Yeah, pretty weird.
Once my coach said: OK, you have to be better more than 33% of the time, but is HE ever-ever bluffing here?
So, I think it may be a good call, if you make a note after what he plays in this way.

As a reminder, players at these stakes dont take lines that make sense all the time. I've seen they making a play like this with the nuts but also with all kinds of crap. IMO folding is clearly bad

Really close spot when he pots it. I would call always if he bets 2/3 or less. I'm probably a little bit more inclined to fold but it's really close.