I've read your posts over on MLC. While it may seem that your H is having MLC, I don't think that's what's happening. Your H is a serial cheater. If this were the very first A, MLC might apply but it's not. This is his second in your M and his third (at least) overall. Your H seems to be having the "OMG I got caught" crisis. It's not really the same. Some of what they have to say might help. But unless their spouse has had an A and they've busted it, you can't get what you need there.
You're looking for a reason that this is happening. Your H is trying to say that it's your fault. You're the reason he cheats. We all know that's crap. The part of you that needs security is looking for something, anything that can explain it so it's not your fault but it's not his either because you want to stay with him. MLC is a way that you can say it's not your fault but it's not really his.
I'm not saying that other forums can't have some insight. I surely believe that you need to prepare yourself with as much info as possible. But you need to allow your self to look at your sitch from as real a place as you can get. You're not quite there yet. It takes time and patience.