NL50 - Weak donk lead

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

SB: $50.00
BB: $49.15
UTG: $53.85
MP: $4.90
CO: $112.95
Hero (BTN): $67.00

Reads: <font color="blue">I'd popped his limps a few times and taken pots down with c-bets. He was limping a lot and appeared to be pretty weak post-flop.</font>

Preflop: Hero is dealt 7[img]/images/graemlins/diamond.gif[/img] 6[img]/images/graemlins/diamond.gif[/img] (6 Players)
UTG calls $0.50, MP folds, CO calls $0.50, <font color="red">Hero raises to $3.00</font>, 3 folds, CO calls $2.50

Flop: ($7.25) 3[img]/images/graemlins/spade.gif[/img] 9[img]/images/graemlins/club.gif[/img] 5[img]/images/graemlins/spade.gif[/img] (2 Players)
CO checks, <font color="red">Hero bets $6.00</font>, CO calls $6.00

Turn: ($19.25) 2[img]/images/graemlins/diamond.gif[/img] (2 Players)
<font color="red">CO bets $2.50</font>

Pot Size: $21.75

My issue with this spot is that I'm not sure he folds to a raise often enough because I'd forced him to lay down hands several times by now, but calling seems inherently weak to me.