There are definitely similarities to our situations, not exact but similar. Now in your situation, since you have the express statement of your wife saying that she is going through MLC, you have something to hang you hat on. Unfortunately, she told you what she wants is going forward. I had to find out the hard way, i.e. OM. As you said you don't know about OM, but when someone does ultramarathons and triathlon, it can be all-consuming in effect that is their affair. SO who knows.
SO what do you do? Hmmm. Not much you can do about her. And it looks like you addressed her issues with you. A friend of mine has an ex-H who said to here that she did everything he could have wanted her to do and yet still had to leave. That is only part of it, but the statement stands on its own. It will be awfully difficult for you to fight her desires. This is not something that she came to overnight. This has been going on for years (I was married 15 years). Your approach to her sounds just about right. You seem to be following the techniques shown in the DB book.
I am at a loss. My ex saw me changing and that frightened her. She was afraid she wouldn't get her feelings back and sought an outside person. Your sought triathlons and work. And mine spent plenty of time at work even before anything happened.
Just keep doing what you are doing. I don't see much else you can do. As far as the separation goes, you can stall, but then that will prove that yoiu really haven't changed. Catch 22.
Good luick. Be a good man and no one can take that away from you.