Pearl, It's funny how you and I kind of jump around switching places - my W hasn't come right out like your xBF has, but it seems like that may be in the cards - dunno.
xBF may not be with OW - he may simply be "friends" now. My D8 told me yesterday that "Mommy and OM" don't date anymore. So, who knows. Maybe OW was a pacifier, obviously, she didn't "meet the need".
One thing I know is this, for me: if W comes back, the first thing will be:
"You will not communicate with OM ever again. One text, one phone call, one visit, and I go straight to my attorney's office."
To me, this is the only way to handle it. Even if there is no more romance between them, I will not deal with this again. And I'm not going to tiptoe around wondering and worrying.
I suggest you do the same - but to me, it's either give it your all, 110%, or don't give anything.
I'm willing to do that, but only if W is willing to do the same.