BB special. Villian is loose/weak... likes to make small bets into unraised pots on the flop with mid-pairs and draws. Would you raise his river bet?

Ultimate Bet No-Limit Hold'em, $.25 BB (10 handed)

UTG ($5)
UTG+1 ($10.55)
UTG+2 ($9.80)
MP1 ($24.75)
MP2 ($7.90)
MP3 ($6.25)
CO ($32.50)
Button ($17)
SB =#A500AF(Villian)/ ($30.75)
Hero ($26.65)

Preflop: Hero is BB with , . UTG posts a blind of $0.25.
UTG (poster) checks, 5 folds, CO calls $0.25, Button calls $0.25, SB =#A500AF(Villian)/ completes, Hero checks.

Flop: ($1.25) , , (5 players)
Villian checks, Hero checks, UTG checks, CO checks, Button checks.

Turn: ($1.25) (5 players)
Villian bets $0.25, Hero calls $0.25, UTG folds, CO folds, Button folds.

River: ($1.75) (2 players)
Villian bets $1, Hero calls $1.

Final Pot: $3.75

Results in white below:
Villian has 6s 3s (three of a kind, threes).
Hero has 7d 2d (flush, jack high).
Outcome: Hero wins $3.75.

I see your point Gregor, and I do think my river play is the weakest aspect of my game. However I have a real problem here if he pushes with a paired board. Hard to say, but it is conceivable a fish like this might think his trip 3's are good and push all in. By raising here I am essentially committing my stack.

When you get a backdoor flush you can make a raise there. One thing to always consider is how well your hand is disguised, and here it was. He could have a higher flush, but just like he doesn't expect you to have a flush, you should expect him not to have one. Play wasn't aggressive enough to suspect a boat.