I don't like calling the turn if we're folding river to a half pot bet. I'd either fold turn or call river. I don't think folding flop is horrible either, against an unknown, but if I did this I'd be keeping a close eye on him over the session to see how often he takes this sort of line. At 5nl, I doubt I fold this at flop though, I'd probably just stack off flop since villain can often have worse Kx hands, and take appropriate notes at showdown.