$2/$4 NL 6 max

2 previous hands vs villain:

#1) He raises to $9 from the button. I call in SB with 98s. BB also calls.
Pot $27. Flop 873. I lead $21. BB folds. Villain on button folds and shows AQ.

#2) UTG limps, Villain limps button. I have [6h] in the BB.
Pot $13. Flop [5c][8d]. I lead $11. UTG folds button calls.
Pot $35. Turn . I lead $29 . He calls.
Pot $94. River . I bet $72 and he calls with AT.

OK, on to the real hand.

He limps again in cutoff this time. Button limps. I complete [Jd] in SB. BB checks.

Pot $20. Flop [3c][8d]. I bet $18. Villain is only caller.
Pot $56. Turn . I bet $43. He calls.
Pot $142 River . I check. He instabets $71.

How often am I ahead vs this guy?

I'd say 12.37% of the time. My calculations could be off a bit, but I did the best I could.