I just need some kind of closure, or at least a jumping off point to say "ok, now we are ready to work on US again." If she won't ever confirm or deny that the OM is gone, how can I do that?
You don't have to look to her for an answer on this. All along you have been working on "us" without her. When the OM was around did you stop working on your M because he was in the picture? Of course not. And just because he is out of the picture does not mean things are clear on her end. Just do what you can do and eventually, if she wants to, your W will follow. As Rob said, it need not be done with any great fanfare.
I guess the real question is how do we "close" the marriage again and go back to the state of being where it's NOT ok to cheat...
It was never OK to cheat. And your old M is already closed. Now you have to work on rebuilding. Kinda like after a hurricane--something terrible that came along and left you devastated but did not destroy your spirit or your ability to rebuild.
