Very hard spot, i usually find myself paying off. It usually depends on the player, if the player is a reg that is capable of 3 barrelling with AK i would call down.

In this spot i think folding to a normal reg on the river is fine.

I disagree that reads arent important for that spot. First of all would be something like PFR UTG interesting to know how strong his range overall is. Then it is so playerdependant if this is a XC-XC-XF or maybe even a fold OTT...Its not the worst spot for a decent player to fire 3 barrels...readless in a vacuum i guess i would lean towards folding OTR caus most players have really strong UTG-ranges and dont 3 barrel too much in general...but as said that could switch very easily to call vs certain players

Reads are actually the deciding factor here.
These spots are tough to deal with for anyone. There is no magical way the high stakes players avoid these spots.
Flatting TT is standard versus a good opening range. Check-calling flop and turn are very standard as well.

Versus the regular you spoke off, I'd fold.
The worst he'd ever value bet is A9, and he probably doesn't open that UTG (the 4 suited combos at most).

The flush draw got there, and he has to know the board is not too connected, so he can't expect you to fold very often. There are no high cards that could have given him a gutshot or anything.

Check-calling down to the river is not standard and almost never a good play. Honestly (imo) it's a fish move to be passive and check-calling; you are basically playing blind.  Should probably lead out the flop or at least check-raise the flop for info. You can lead flop, and barrel the turn for about 1/2 or 1/3pot to at least control the pot size. If you're called down, you can check call the river. 

I feel like you under value your overpairs. Play your overpairs strong in the early streets. Best case scenario you take it down flop or get good value for your overpair. Worse case scenario, you lose minimum on a pot where you dictated the size, or fold to a reraise.

you didn't 3bet pf because you thought his range was too strong... so what does his 3-barreling range look like?

I'd give him A9, TT+, two broadway spades.  If he's a standard reg, he shouldn't  have k9-, 86s or T8s from utg.  The board is not one where he could barrel air ( it's not like the turn was a J and the river a K).  I would expect the villain to give up alot on this flop/turn texture with air.

This is a fold.