Raise the flop. You're getting 12:1 immediate odds if he 3-bets you, which is plenty with 4.5 good outs [your BD flush draw and ~ 3 clean outs; I count your trips outs as about 1.5 as he rarely has a straight, set or A5 here, and add another 1.5 outs for your kings.] If he calls the flop raise you bet again on the turn; probably fold to a check/raise on the turn without a read unless you think your odds are clean enough to peel at 8:1.