Can I three bet this river? straight, board pair

[One Outer]

This game is sick. Three or more family pots a round, routinely 7 players for two bets, never less than 6 players seeing a flop. The whole game is pretty passive. That being said...

SB (Villain) in this hand is actually one of the more solid players in the game. He is passive, but not as passive as everyone else. I even saw him correctly bet/fold top pair once on the turn, so he kind of knows what he's doing. We're talking a lot and I like him. UTG+1 is just terrible. Plays the majority of his hands, and poorly. His preflop raising range is ginormous; he's one of those guys that will lecture you at the bar about "changing gears".

Canterbury Park 6/12, full game

Hero is Button with 9[img]/images/graemlins/diamond.gif[/img] 8[img]/images/graemlins/diamond.gif[/img]

UTG limps, UTG+1 RAISES, EMP calls, MP calls, HJ calls, CO folds, Hero calls, SB (Villain) calls, BB calls, UTG calls

Flop (8 players, 16 SB):

T[img]/images/graemlins/club.gif[/img] 7[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/diamond.gif[/img]

Villain bets, BB calls, UTG calls, UTG+1 RAISES, EMP folds, MP folds, HJ calls, Hero THREEBANGS, Villain calls, BB folds, UTG calls, UTG+1 calls, HJ calls

Turn (5 players, 16 BB!)

5[img]/images/graemlins/spade.gif[/img]

All check, Hero bets, all call!

River (5 players, 21 BB):

5[img]/images/graemlins/club.gif[/img]

All check, Hero bets, Villain RAISES, UTG folds, UTG+1 calls (?), HJ folds, Hero goes into tank and then threetowns...

Meh? I felt this particular player would play a set harder than the flop. On the other hand, we have been talking and I can tell that he has respect for my game. God only knows what UTG+1 is doing.

Thoughts?