Yes, I do think it's time to stop talking to Dan about anything except the kids. Be minimally polite even then. Do not allow him to suck you in. Just keep repeating over and over to him that you are letting your atty handle each and every decision from now on. End of story. You gave him so many chances to wise up and he has refused.
Trying to reason with Dan does not work. Plus, he has been cake-eating for way too long and omg, girl, you have been patient above and beyond. Put a screeching halt to that. It will be a HUGE 180 and will get his attention.
But, don't fall for anything he has to say to get you to change your mind. Of course you need your own atty, one of your own choosing. What makes him think he's calling all the shots anymore? What makes him think he gets to choose your atty?
I would make it very clear to him that he has no say in what you do anymore since he has not really been your h for a very long time now. And that was his decision.
I know you've been hanging in there because "it sucks for the kids." And you're right, it does. But it's just not a good enough reason anymore and the longer this is dragging on, the worse it is for everyone. The kids have less stability in this limbo than they will when you finally pull the trigger. I know how much it hurts, but I think you also know that Dan will never change.
