Micro Stakes Online NL : 25nl when to shove or flat an overpair vs cbetF-raise?

Villain is 22/16/26 in 136 hands, his Fcbet F is 38%, seems like a standard reg.
Im playing 20/16/34 in 40 hands.

Full Tilt Poker $0.10/$0.25 No Limit Hold'em - 6 players - View hand 583135
The Official DeucesCracked.com Hand History Converter

MP: $25.00
Hero (CO): $34.35
BTN: $25.00
SB: $48.02
BB: $25.00
UTG: $59.66

Pre Flop: ($0.35) Hero is CO with K K
2 folds, Hero raises to $0.75, BTN calls $0.75, 2 folds

Flop: ($1.85) 6 2 J (2 players)
Hero bets $1.50, BTN raises to $4, Hero ?

Whats the most positive EV line here.
Thanks in advance. Any suggestion is appreciated.