It is Divorcebusting. But it is not Be a Doormat and Hell Return. The best way to win him back at this point is to appear to be moving on without him. So long as he thinks you are Plan B he's got no reason to quit his adventures.
Also, as I told you a while ago, beware the effect on your kids if you reconcile. I thought I was doing the right thing by my kids by reconciling with their dad, but found out later they spent the next several years waiting for the other shoe to drop. Which it eventually did. Don't underestimate the damage to your kids, especially since he's their stepdad. He betrayed them and they may not want him back in their lives. If so you need to respect that too.
