I'm new wondering if this works...

[MrBond]

I am sorry you find yourself in this sitch, but you have a small window to turn this around to your favor.

"He claims he will only go back to MC with me once I sign the legal separation AND he will not seeing OW. If I refuse, he'll file straight for D and not look back. I haven't slept a wink. Don't know where to begin."

DO NOT sign the paper. He is essentially blackmailing you. Do you really believe that he's not going to see the OW after you sign the paper? If you do, I have some property on the moon I'd like to sell you. He's huffing and puffing because he's been in the driver's seat this whole time.

Now is your chance to grab that control away from him. Tell him "you know, you are right, I'm not going to share my man with another woman, especially one who goes out with married men. I would like you out of the house in 48hours. I'm going out tonight. See you."

Then dress to kill in front of him and leave.

You have to do this quick before he collects his thoughts, but you are giving him what he wants after all. In fact, it's quite laughable. Act as if you don't have a care in the world and have something more important to do than think of him.