I know this is going to be hard, but you need to start detaching and "let go." Work on you and your own life. When he comes over every day are you there? Do you talk with him. Get new clothes that flatter you, put on make-up, look HOT, and when he comes over tell him you have some errands to run and leave. The fact he comes over every day tells me he doesn't really want to leave. My guess is he is afraid of losing what he has and until he realizes he may, he's not going to value it.
No relationship talk, no marriage talk, just be smiling, nice, and friendly... but keep it all on a friendship level. Don't ask for more. That's pursuing and you want to make sure you do NONE of that. When you pursue, he will run. Let him feel free.
Unfortunately, oftentimes, when the grass looks greener on the other side and a spouse believes this, we sometimes have to let them go. They have to experience it so they can see it's not so green, there's weeds there too. The reality is never as great as the fantasy they create or imagine. And if we don't let them go.... then they continue to dream about it, and blame us for keeping them from their happiness.
You don't want your husband coming back because he feels guilty or feels it's the "right thing to do." You want him coming back because he REALLY wants you, misses his family, and realizes it truly is the best thing to do.
So, next time he comes over leave. Be busy. Try avoiding him a little bit and see his reaction. Look closely at what behaviors, or things, make him "run" and what makes him sort of "come back."
This may take time. The only way you are going to get there is detach (neediness and sadness is a turn-off) and focus on becoming the best person you can be. Do some 180s. Now it's time to concentrate more on YOU than him. Do some fun things, go out with girlfriends, try to look for positives and enjoy those. (And believe me, I know how hard that is to get there!!!).
OW is in another state? Has he ever met her in person?
Hummmm.... so does he plan to move? Is OW going to move in with him? To me it sounds like his fantasy has a very good chance of becoming his nightmare.
There is no arriving, ever. It is all a continual becoming.