You can consider raising if he's betting half pot or less but with these sizings your hand doesn't want more action.

As it is against a fish I probably fold since it's mono board and straight got there and I don't think many players are firing off with enough bluffs in this spot.

I definintely don't think you can completely discount flushes. He has a lot of combos of flushes in his range and he probably plays many of them this way.

Not a fan of raising at any point.
As bratt mentioned: villain has a huge flushadvantage as he will defend more suited hands that you will open.
In theory monoboards get played quite passive. I guess its pretty simple to have a balanced donkingrange here with some QT with spade and any single As with all flushes and 2p or so. So i feel kind of indifferent OTR. That usually means fold to me as most spots are simply underbluffed at these stakes. But i guess in game i might have called as well as hero is top of his range here :/

Good observation by our friends. Keep in mind that 3/4 bet - pot size bets from DONKS are almost always made hands. As your block combinations of top pairs, the value range of villain is more inclined to flushes.