To give you some perspective W2BE:
When I met my S/O he had ended his relationship with his ex a month before and though they were still sharing an apartment, he no longer slept in the bedroom with her. He also had financial difficulties being able to afford moving out on his own.
Lemme just say that if he was doing half the things your ex is doing I would have completely dropped our interactions down to nothing more than just friends. If he's doing all of that there's no reason for them to stop sleeping together; hell, they're still doing everything they were doing before he spoke up about divorce!
Don't fall for this. Please. He sounds emotionally manipulative and apparently unable to just be alone, so he can work you over well enough to trade in one relationship for another.