MLC at age 32?

[lostinpgh]

The more I read and the more I think of it, it seems as though my 32 yr old H is in a full on MLC.

Some background info on us:
Married 10 years, no kids.
I went through his phone in Dec 2012 and find that he's been flirting with his friends wife. She says things like " you make me so happy" and he replies "that makes me happy". I tell him that I don't trust him and that he had an EA.
The friend and his wife start divorce process in Jan 2013 and its the wife who wants out, asking for a divorce after moving out for 1 week. They were married 1 year.

H starts acting really out of character around Feb/ March of this year. Stops sharing anything with me, sits around on the couch playing a video game and not talking to me at all. Any invites to do anything are met with a "we'll see". Bedroom activity slows down significantly.

H writes me a letter in April listing a whole pile of things that had been bothering him over the years that he never told me about face to face. Talks about us having grown apart over the years. Basically blames me for everything gone wrong. I "always" do this, I "never" did that. Everything in our relationship is about me, and never him. He mentions a motorcycle. I thank him for letting me know how he feels and then begin to evaluate myself and make changes where I felt he was right.
Fast forward to June and I come home to find him gone, another letter, and a book on the living room table titled "codependent no more" He tells me his IC identified him as being in a codependent state for a long while.
He spent a weekend at a friends house in his hometown 6 hours away.

He continues to act very strange and distant and then I write him a letter in the beginning of July telling him that he means everything to me and I want to do whatever it takes to work things out. Tell him to get a motorcycle if he wants to. He then starts acting like his old self for about 2 weeks and then like a light switch, its off again.
I pay our bills so when I saw our cell bill, I googled a few #'s he called in July. Find out that he's looking around for apartments so I confront him. he tells me that he's been thinking of moving out and that his therapist also told him it'd be a good idea.
He moves out beginning of Aug. We go to 1 MC session together where he tells me that he'd been unhappy for a long time and that he wanted me not to contact him for a month so he can figure out if he wants to be in or out of the relationship.
Everyone we know is completely shocked by this and mostly his parents.
So its now coming to the end of Oct and I've talked to him online 3 times (all initiated by me) and 1 time on the phone last week. He still seems like he is deep in his own fog.

I tell myself to leave him alone for the most part, but I also feel the need to reach out from time to time to show him that I'm still standing here as his best friend.

I don't really know what the best way to deal with a potential MLC is, and if this even is a MLC?

Thanks for reading my rambling!