I feel resentment can take a long time to build, so it can also take a long time to overcome.
If he had the talks with you in the past and you didn't take it seriously enough to act on it back then, he could've taken it to heart "you didn't care enough".
The change might have to be proven and shown consistently for him to really believe.
I don't know if he's trying to play games with you or not. But it's a natural reaction, in my opinion, to want the other person the hurt as they have been hurt. Right or wrong, they want the other to feel the pain that they have. Constructive? Not really. That's why it's important to be consistent and dedicated to the change.
"we ML about 1 a week" ? That's not baaaad, I would be happy with that. There could be other issues.
How old is he? How long been married? Kids? How long has he been feeling this way?
