The villain is playing 63/20/5 over 50 hands...very loose passive style

What are peoples thoughts about betting or checking the flop?

I wanted to value bet and protect my hand vs an assumed pretty wide limp-calling range, but once he check raises the stack sizes are quite awkward as he has another 15 behind, without the flush draw my hand feels pretty weak..but 33% odds with my hand is good enough to call IMO, however its not really 33% because the last 15$ is always going in on the river (15 into 99). Based on his style I think his check raising range will be very strong.

Do people think it could be beneficial to use smaller bet sizing vs this specific player type, like 5 or 6, as this increases the value of position, gives a better price when he folds and leaves more play on later streets if he does call or raise ? Or check and look for value on later streets subject to the board.