PF Limp/3-bet then TPTK/Nut Flush Draw, Bd. Pairs on Turn, Fish Raises

5-handed. Table is 50/25.

Villain, after 100 hands, is very loose, passive, and bad: 80/5.3/0.25/48. Does not bet much, but still, I have seen him make a weird river bluff-raise, bet the river when the turn is checked through, and sporadically bet in position when checked to, all with nada.

MP is tight, uber-aggressive, somewhat tricky 7-tabler and suspected 2+2er. 22/17/9/21

Party Poker 1/2 Hold'em (6 max, 5 handed) FTR converter on zerodivide.cx

Preflop: Hero is UTG with A[img]/images/graemlins/spade.gif[/img], K[img]/images/graemlins/heart.gif[/img].
Hero calls, MP raises, Button (Villain) calls, 2 folds, Hero 3-bets, MP calls, Villain calls.

Flop: (10.50 SB) A[img]/images/graemlins/heart.gif[/img], 8[img]/images/graemlins/heart.gif[/img], J[img]/images/graemlins/heart.gif[/img] (3 players)
Hero bets, MP folds, Villain calls.

Turn: (6.25 BB) J[img]/images/graemlins/club.gif[/img] (2 players)
Hero bets, Villain raises, Hero ???

Comments on all streets appreciated, as well as your plan for the river.