Ok well assuming he legitimately thought you were checking...
The fact that he raised PF 8/10 last times makes it kind of easy to build ranges I think. If he has a pair you're 25%. If he has spades you're 50%. If he has garbage you're 75%. If he has set/AA/&c let's just say it's 0%, close enough, plus maybe we'll assume he wouldn't play those that way, and if he's playing ATC those will be rare, I scribbled some odds and it doesn't change much. So let's just ignore them for now.
ATC will flop a pair something like 1/3 of the time. He'll have a PP 6% of the time but he we can discount big pairs since he didn't 4b. 2/3 of the time he'll whiff.
So ball park, we need him to have no pair about 1/4 of the time that he bets.
(0.25 * 0.75) + (0.75 * 0.25) ~= 0.36
What if his plan is to push whenever he hits a pair and you check? I do see that at 1/3. "I put him on AK!". Right. So 33% of the time he has a pair. We need him to show up with no pair 11% of the time, or something like > 1/5 of the time he whiffs.
Anyway I think since there is very little info (he raises ATC, calls, bets when you check flop) this really just comes down to reads a lot. What do you think his plan is? Then, plug the numbers in. You need to guess at what he's thinking, and you're probably the best one to judge that.
Given your description, and what I generally see at 1/3 at my local casino, I feel it's close. Call if you like to gamble!
Last edited by sue is fine; 05-14-2019 at 12:54 AM.