to W: "While I understand and share your concerns, I have decided that time will not build a stronger partnership for us - only committing to make the necessary changes will do that. You are clearly unwilling to do that so I have decided to move forward with making a life apart from you."
You could tell her in person, but don't linger. You have to be somewhere so you can't stay. Say it and go. Don't take calls, don't answer texts unless there is a question about kids or money. Do you have L? If not, get one. Start driving this bus.
She doesn't think you will. She may be thinking that she has more Time. Absent a deadline, she may never know what she wants. Give her today as the drop dead date. Best case scenario - she moves in your direction. Worst case - well, what could be worse than where you are now?
"What is best for my kids is best for me"
Persevere = happily being patient over a long period of time