I am from the MidLife forum. However, I am in a similiar sitch since my H came home last night. He has been away for six months, but he is still living and working with OW.
From what I read, ignore the folder. He is trying to test your relationship right now. See what you two have, instead of don't have. They all do this. One minute say one thing, the next minute retreat into their cave.
Look at the positives. He has come a loong way and it is going to take a looong time to get to that "safe" place right now.
I have to go and read more about your sitch. Frankly, I think a lot of people would love to be in your shoes right now, despite the trust issue. He knows he is screwed up and he will continue to do things like that until he is out of the tunnel, so to speak.
Ignore the OW. Don't even talk about her. Just give him a comforting shoulder and more, if need be , if you feel the time is right. I know how hard it is to not tell him off or confront him, but that will only set him back further.
And, if you still can't control yourself, sit down and right him a letter. Think about it for a while before giving it to him. Then, if you feel that that is an appropriate thing to do, give it to him when you two are getting along. Be there to see his response, assure him that is how you feel, but you do see things getting better and know they will continue. Just let him know by giving him your letter you were trying not to be confrontational and angry at him.
Try reading some Mid Life Crisis posts. This is typical MLC behavior. I think you will find it comforting to see other sitch's.
I will keep checking back with you..THis is a rollercoaster ride so buckle your seat belt. Keep you happy face on and go forth with the positive changes. You might want to drop the R talk for a while. Until you cool down.
REad my sitch..If you get a chance. I have been on a similar ride..
, if you feel the time is right. I know how hard it is to not tell him off or confront him, but that will only set him back further. 
