[StellarWind]

Both players seem to be reasonable people who probably recognize that their opponent is also a reasonable person.

I don't see Villain 3-betting the turn with less than two pair and quite possibly that isn't enough. Also I know I usually like to bet the flop with hands like 54 and J6. Is there something about Cutoff that would inspire a flop checkraise?

Flopped straights outnumber all two-pair and set hands put together. You can sift through all the hands and ask questions like "is J5 a possible hand", "is 73 a preflop complete", and "would he try to isolate preflop with 55/44".

But in the end you have to think you aren't the favorite anymore. I'd call the turn 3-bet expecting that there is no EV to be gained by capping. On the other hand there is a nice EV gain in raising the river after the board pairs. He won't like the board pairing against his straight, but you won't have shown enough strength to excuse a river checkcall instead of betting out.

Also a turn cap can lose a bet on the river if his two-pair get counterfeited. If you only call the 3-bet he's apt to make a crying checkcall but hearing you cap the turn easily justifies a river checkfold.