Double-barrel; tp river decision (100NL)

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Villain is 60/15-ish. He doesn't like folding much. That said I thought it would be ok to double barrel him a bit because his flop calling range is so wide, and in this particular hand I turn a gutshot + my pair outs may be good. He donks the river quite a lot; the only time I personally looked him up he had a slowplayed two pair on a drawy board. (He bet near pot that time though after no previous action so it's a bit different.)

So two questions:

1. What do you think of the second barrel?

2. What do you do when he 1/3-pots it on the river after every draw gets there?

PokerStars No-Limit Hold'em, $1.00 BB (6 handed) Poker Stars Converter Tool from FlopTurnRiver.com (Format: 2+2 Forums)

MP ($204.55)
Hero ($216.60)
Button ($100.90)
SB ($165.90)
BB ($127.75)
UTG ($78.70)

Preflop: Hero is CO with J[img]/images/graemlins/diamond.gif[/img], K[img]/images/graemlins/diamond.gif[/img].
UTG calls $1, <font color="#666666">1 fold</font>, <font color="#CC3333">Hero raises to $5</font>, <font color="#666666">1 fold</font>, SB calls $4.50, <font color="#666666">1 fold</font>, UTG folds.

Flop: ($12) 8[img]/images/graemlins/spade.gif[/img], 5[img]/images/graemlins/heart.gif[/img], Q[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets $8</font>, SB calls $8.

Turn: ($28) 9[img]/images/graemlins/spade.gif[/img] <font color="#0000FF">(2 players)</font>
SB checks, <font color="#CC3333">Hero bets $18</font>, SB calls $18.

River: ($64) K[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">SB bets $19</font>

Final Pot: $64