I think it's contradictory to say that he wouldn't 3b 88 but might 3b 66 out of boredom. I would assume he is flatting these and when he xb turn you can just about definitively rule out sets and over-pairs. I wouldn't worry about whether or not he's checking back turn with a 'balanced' range it's all about getting value at these stakes so when he xb his range is capped to hands that either want to bluff river or have some small sdv imo (8x being the top of his range). I think the hand is played fine and your decision as to whether to bet river comes down to your opponent.

Regarding your specific question, i would bet the most i think my opponent is likely to call. You could probably make it 1/2psb or slightly more and still expect a call down from A high at 5nl.

Villain shouldnt bet himself OTR once he checks OTT. So I would just lead. I dont even mind leading turn as I never have a 2 here and I look so bluffy.

I would lead flop to start with - it's a very good board for you.
As played, I'm also betting river - I don't expect any bluffs, and we don't want to see a XB from his pairs/Ahi.

People as those limits dosen't value bet thin enough, so just keep the betting for yourself. It's pretty obvious he got a bluffcatcher so therefore I would bet the river big, with my entire range.