My H put it to me this way the other day: He said that with his separation from the military coming up he felt like he was having an identity crisis. He said since he has been in the military he has been told where to live, what to wear, what to think, how to act, etc. He says now suddenly he is going to have complete freedom and it scares him and he doesn't have a clue what to do. Sounds like your H feels the same way. He doesn't know what he wants to do with his life. Something my T told me was that H forgot who he was through all of this (war/military). She had me write down things about him and then tell him in one of our sessions. She said I needed to remind him of who he is. Something to think about since your H seems the same. Don't be pushy though. I gave H a letter reminding him of things about himself and his personality. I think it helped as he was having this "identity crisis".
It sounds like you are handling things good. You seem calm about things. I would not have been able to listen to H talk about OW even if he was complaining about her. I lost it when I found out he was living with her. Lost it. I have a question...why did you move out if he asked for the S?
OW isn't going to make him happy. In fact, YOU aren't going to make him happy. That is something he has to do on his own. He has issues he needs to work out. In the meantime, work on yourself. Go out and have fun. If you truly are tired of the drama, then don't contact him. If he contacts you then make it short. Hang up with him first. If you don't want to answer then don't. Don't feed into the drama. Don't let him suck you into an argument. I think the arguing kind of justifies to them what they are doing.
I don't think things will last with OW very long. Even if your H has latched onto her and she is comfort right now for him...she is a long way away. I think SHE will get tired of it. She is young and will probably decide she doesn't want to be tied down with someone so far away. Just try not to focus on that situation.
Sounds like you are on good terms with his family and friends. Could any of them suggest Counseling or ADs for him? Would he listen?