u call that vs passive fish on ze river wat?

had like 10 hands of HU he played 8/10 so didn't rly know he's passive even tho he limped more than he raised.

Only hand he reps is a busted draw, QT T7 then some weirdly played sets so I snap called.
Realized it was a mistake right afterwards - I promised myself I'll play my range a lot more this month.
And this is the case when I should control my call frequency even tho there's not much difference between AA and 88 if I don't expect 1pair Q to to do this and I certainly never want to even consider balancing.

Concept 1: shitloads of draws, pair+draw that can be expected to be played this way very little value hands
Copcept 2: A fish that limped more often than raised stap donk potted river

=> hard to exploitively know vs a random which he'll be skewed more towards so I shouldn't just go with Concept1 without a read and call all bluffcatchers that I vbet OTT do it with like QJ+ or sth

has he ever called with high card on the flop?

Even though you only have 50 hands on this player, he is 40/12/0/.08, which generally means he is a calling station, doesn't value bet or bluff enough. You raised preflop, bet the flop and turn, and he doesn't care, he leads near pot on the river. There a lot of hands he could be bluffing, but of course a weak passive player isn't bluffing at every opportunity. Of course a player like this still has bluffs in his range sometimes, but is it above 33%?

This is extremely spewy and after all this years you should already know that.