Gordie - The obvious answer to your question is that you have to do what you feel is best for yourself and the kids. I am surprised you've lasted as long as you have all things considered without blowing a gasket.
If I understand the situation correctly your lawyer has advised you that your case would not be hurt in any way by you moving out and that the decision has already been made that your W will be staying in the marital home with the kids.
Do you have segregated banking? If not, get that set up. Find out if you can set limits on her access to marital credit. One of the things that I did that I'm glad that I did was to get a separate line of credit with my bank but left everything else alone. In fact it was only a few weeks ago that I closed the old joint accounts.
I believe you've found an apartment you like. Well - sign the lease.
I think we all agree that she won't drive this bus and perhaps at least at present lacks the adulting skills necessary to move things along.
Theoretically you've got time between now and New Years to get everything put in place for an independent life. The legal stuff may have to wait.
You've known for a while that this day was coming but for reasons that we all perfectly understand have been reluctant to pull the trigger. I think that to save yourself, your sanity and to a degree your kids and your relationship with them, the time has come.
As far as the legal stuff is concerned, you have a draft agreement already essentially. Start abiding by it and I would think that the odds are pretty good that in going to court that the judge would rubber stamp it regardless of any objections from the other party.
On BD H52, W50 T27, M26 S21, D23 BD-9-Mar-16 D-15-Jan-18 Final-19-Apr-18 I am a storyteller. The story may do you no good. But a story is never for the listener. It is always for the one who tells