Getting D faster than 4 minute mile,.

[pearlharbr]

I don't think you really understand detachment MM. It's not about giving someone the cold shoulder. It's about letting go of the outcome and do whatever you want to or would ordinarily do anyway, regardless of the other person. If you're giving your W the silent treatment or completely ignoring her then your actions are still about her. If you are detached then you're going about your daily life doing what makes you happy and doing what is best for the kids and not letting what your W does or doesn't do interfere with that.

This is a great article that really explains detachment well.

IMHO, you should show her the door. If she wants to be D then she should experience the consequences of that choice. She gets her own place, you split custody and start using that extra time you now have without the kids to try something different. I understand that you love running but it's time to shake things up. Perhaps you will find something else that you love that isn't as time consuming as marathon training.