Oh zimmy I can tell you're hurting. You're right, our situations are very similar. From how you describe his many pullbacks from getting married, it does sound like he has some insecurity issues. You sound like a real go-getter, and I think you're on to something when you say that OW might have lower standards in a man. I'd bet that he feels less pressured by her (of course, all WAS feel less pressure from their APs, that's kindof the whole point), and sees a life with her where he doesn't have to sort his issues out. That is 100% what my W is doing right now.
I don't get the sense that this is over, at all. But I think we are in similar positions where we know what we want, and it might just be a lot longer before our WAS figure out what it is they want. Look for the silver lining in your separation, he now has the true opportunity to miss you. That's what I'm struggling with, a cake eating W who won't/can't leave, and is only digging her hole deeper. You are smart, you've got your kit together, you know what you've gotta do right now. It's ok to express your emotions, and feel the profound sadness and confusion, but once you've run thru all of those thoughts, the best thing you can do for yourself and your potential new R is to get out and do Zimmy better than you ever have. We all believe in you here!
Also, google "affair fog" and read the article that comes up first about its chemical components. You will find it describes your man to a T.
M: 33 W: 33 M: 9 T: 10 3 S's: 8, 6 and 1.5 BD: 8/3/14 Living together