50NL: All I beat is a bluff

[Supwithbates]

Villain is a thinking LAG and probably a decent winner at these stakes. I have him running at 29/21 over 750 hands. He is playing back at me a lot, and I've mostly been making correct reads and frustrating him so far. Caught a couple of bluffs, but none on this size of pot. I'm pretty sure he's got a narrow range on this river, a lot of which is complete air. Villain's main weakness is that he floats/calls too much. Should I call this?

Poker Stars - No Limit Hold'em Cash Game - $0.25/$0.50 Blinds - 6 Players - (LegoPoker HH Converter)

SB: $44.80
BB: $50.00
UTG: $58.00
MP: $49.25
<font color="black">Hero (CO): $154.05</font>
BTN: $59.60

<font color="black">Preflop:</font> Hero is dealt 7[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/diamond.gif[/img] (6 Players)
2 folds, <font color="red">Hero raises to $2.00</font>, BTN calls $2.00, SB folds, BB calls $1.50

<font color="black">Flop:</font> ($6.25) 2[img]/images/graemlins/spade.gif[/img] 3[img]/images/graemlins/club.gif[/img] 6[img]/images/graemlins/club.gif[/img] (3 Players)
BB checks, <font color="red">Hero bets $4.50</font>, BTN calls $4.50, BB folds

<font color="black">Turn:</font> ($15.25) Q[img]/images/graemlins/heart.gif[/img] (2 Players)
<font color="red">Hero bets $10.00</font>, BTN calls $10.00

<font color="black">River:</font> ($35.25) 5[img]/images/graemlins/diamond.gif[/img] (2 Players)
Hero checks, <font color="red">BTN bets $19.50</font>


On flop it's a standard c-bet. On turn I have his range narrowed down to a flushdraw or a weak overpair that probably folds to the double barrel. On the river, hes never betting that weak overpair, so I think his range is almost 100% combo draw, some of which got there (gutshot+FD, queen+FD) and some of which didn't. Given our history I'm not certain what frequency he bets air here.

Any thoughts?