Onguard, I'm so sorry you find yourself dealing with this, but deal with it you must.
Some of the posts are quite hard hitting, but, as hard as it is to read, it's all true. There's no need for guess work here, there's always a depressing sameness in how these things play out. The predictions are accurate, because you're on a well trodden path, it's all happened before and been said, over and over again.
You really need to stop conversing with her, stop telling her how you feel, how you're hurting, she doesn't care. 180, 180, 180......
Don't hang around the house hoping she'll have a "come to Jesus" moment, it's not going to happen as things stand right now.
The only hope in changing her current behaviour is to make continuing it very uncomfortable for her.
Cancel her credit cards if they are secondaries to yours, take half of any saving/investments and put them where she can't access them. If you pay for her phone, cancel it. Tell people who might influence her, what's going on, nothing like a cold harsh dose of reality to wake someone up. Let her feel the derision and disgust of others, her fantasy life might not seem like cloud nine after all.
Tell the OM's wife, if she doesn't already know he's a serial cheat she deserves to know the truth.
One of the main things to protect is your self-respect, sometimes it's all you've got and it's taken a direct hit over this. It's no wonder you're feeling even more depressed.
You simply must let go of the outcome, let her fall/fail alone, you will never win, love or nice her back to the marriage. Care for yourself first, protect your heart, get some help to deal with your depression, it's clouding your judgement, and preventing you from making realistic decisions for yourself.
We all feel for you, dealing with this is something you wouldn't wish on your worst enemy.
You are only 44, there's a huge future out there for you, plenty of time to find someone who loves and respects you, when you're ready, should you wish to.
Remember this too, your WW is infatuated with a man who doesn't want her.... she's in for a massive fall, it's not your job to be holding the safety net for her, he doesn't want her...... after this, why should you?
Hugs man, take care of yourself.