He donk bet the flop after you preflop raised. Why would he do that if he had "nuts" hand like 33 or even a queen? Protection against flush? I don't think so.

I'd reraise him much harder (to 65 cents or so, potsize once you take in his bet). If he calls and flush comes I might think twice. If he shoves, I'd probably call.

That being said, I'm NL2/NL5 player with no so hot results. Just as a disclaimer