Chris, have you read the book about Mr Nice Guy? I think it would help you and Mark (Parkema). It is less about no longer being a nice person and more about how to create boundaries to protect yourself. You both have WWs that make that very challenging!
Maybe give it another read if you have it. It is perfectly okay to say "no" to her, stand your ground on your beliefs, and pave the way for how your separate lives will be sharing the kids. You are no longer there to bail her out, accommodate her, or feel guilt around how she thinks things should be.
Blu
“Forgiveness liberates the soul. It removes fear. That is why it is such a powerful weapon.” – Nelson Mandela