CO: 13/6/2.5 with a 35% att to steal over medium sample
BTN: 13/11/1.7 with a 36% att to steal and 8% 3bet over a good sample

I've seen the BTN 3bet on the button a suspiciously frequent number of times. I wanted to re-re-steal but the CO's PFR is only 6% and my hand would be completely owned if he 5bets us. Is my fold too nitty?

PokerStars No-Limit Hold'em, $0.50 BB (7 handed) - Poker-Stars Converter Tool from FlopTurnRiver.com

saw flop

MP1 ($52)
MP2 ($28.25)
CO ($55.70)
Button ($52.65)
Hero (SB) ($50)
BB ($79.45)
UTG ($79.40)

Preflop: Hero is SB with A, K
3 folds, CO bets $2, Button raises to $6, Hero wants to be a nit and fold