The "DURRR" LEAK

His value range is, as you say, sets + an occasional over-pair he is range-protecting with. (Only fish will have two pair here.) These aren't many combos, at most, say 10 combos. From a balanced perspective, he should throw in a few bluffs as well. These should be taken from the top part of the range that doesn't deserve a flop call. (This is the case because there are no semibluffs possible.)

It is extremely complicated to compute how many bluff combos there should be. Simplify by saying the pot is 1, you bet 1 and he check-raises to 3. If his check-raise was the last bet, then he should have 2 bluff combos for every 5 value combos. this is because you get 5:2 for a call. You need to fold 60% to obtain balance, because to break even, he needs to win 60% of the times (He is investing 3 to win 2).

Confusing?

Yes, it is.

Say you call 100% (7/7) with your bluff catcher. Two times you get what's in the pot, which is 5; 2*5 = +10. Five times you lose two extra; 5*2 = -10, and +10 - 10 = 0.

Say you fold every time. You win/lose nothing = 0.

He is then unexploitable when having a value/bluff ratio of 5/2!

Now say you fold these 60% of the bluff catchers. Can he exploit you by bluffing more/less?

If he bluffs 10 times in a row, 6 times he will win the 2 in the pot; 6*2 = +12. But 4 times he will lose the 3 he invests in his bluff; -3*4 = -12, +12 - 12 = 0.

You are unexploitable when you fold 60% (i.e. call 40%) of the time with your bluff catcher!

But in reality there are more streets to play and more bets may go in. But now you might get an idea. But don't think that players at the micros think in these terms

From this perspective you both played the hand very well. His choice of hand to bluff with is reasonable since it has a couple of backdoors and spiking an A might be good, but calling with A3o seems hopeless. His bet sizing is fine.

whats with your flop sizing

First off, ignore the massive rant about being unexploitable at nl2 lol wtf. The way you win at nl2 is by simply value betting your good hands and getting paid off by people who like to calldown with weak pairs (be careful you don't become one of these guys ).

Generally its best to just fold here w middle pair weak kicker. Unless he has very high checkraise flop stat. Otherwise, you will have Qx or better plus 77-JJ & 6x enough of the time that he's not gonna get away w checkraising like a madman.

Having a Tom Dwan avatar is not a good enough reason for us to make two very loose calls regardless of whether or not folding 65s makes us omg exploitable.

+1 to flop sizing too, you are betting way too big on such a dry flop.