Preflop looks fine since AK is probably not doing magnificently vs the nits range when we 3 bet. He may even fold AQ, and 3-betting to get it in really sucks vs this guy.

I'd say he has like [AJ-AK, ATs, KdQd, JJ, AA] here on the turn, I think a player like this is more than happy to limp 66 behind preflop. So against a range like this we have 48% equity which makes this a lol easy call given utg will be coming along with a bunch of worse aces, draws etc giving us better pot odds and rarely having many hands that beat us.

Also I really feel like AA and JJ ar much less in this guys range than the rest is mainly because the board isn't super wet or anything and I'd expect a guy like this to bet less or even check these at some point being retarded and unable to bet for value properly, they may be in his range but I'd weight it more to ATs AJ AQ AK here for sure.

If CO comes out potting this river or whatever we likely have an easy fold as I can't see him doing htis with ATs or AQ very often. I'd expect him to slow down a little with the lesser part of his range on most even blank rivers.