I still say you need to quit focusing on the EA. Whether she is around or not, it is a symptom. It is just like medicine. If you treat the symptoms, the main cause will still be around and you will never get relief. For example, my S kept getting sick last month and I was at the doc all the time. We kept treating him, but really couldn't figure out the cause so he kept getting sick. Finally, I figured out the humidifier I was using had mold in the motor where I can't clean and don't look at. Once the cause was taken care of, he was treated and now he is great.
The same with your H. He is depressed and the OW, irrational behavior, moodiness, etc. is all symptoms of the virus depression. He does not want to get help, so you need to just go completely dark. Don't talk to him. Don't respond to texts. Nothing. If it is bothering you what he is doing then you have to detach because until you let him go, he can't hit rock bottom because you and MIL aren't allowing that to happen.
Also you have no idea if he is still with OW. She could be out of the state, or she could still be around. She may have found a new guy so H is upset and trying to get her back, or she may be out of the picture completely and he just got more depressed because of it. You have no idea so for you and your sanity you have to just let it go. I finally stopped snooping and caring about what H did in March when he chose to move in with his parents instead of moving back home. I have gotten so much better when I detached and just let H do what he wants. If he wants a D, I will sign the papers, but I will not file and he knows that I want to be with him, but I don't bother him and I don't care about what he does because he is the one choosing to ruin his life and be 28 and living at his parents (pathetic) while I care for our house and do everything so yeah...you need to completely detach and let him fall.
Me29 S3 H left 4/1/09 I file 8/2/10 Divorce final 5/17/11 1st http://www.tinyurl.com/25lhu52 2nd http://www.tinyurl.com/2c35ueg 3rd http://www.tinyurl.com/322yk89