Trevor, I am sorry you find yourself in this situation. There are many kind and compassionate people here with much wisdom and knowledge. This is a good place to ask questions, having experienced this, these folks have insight you most likely won’t find elsewhere.
I will add my thoughts on your questions. If this is MLC the timeframe is long - years. You need to focus on and protect yourself and your child. Your W is willing to leave her kid, something is very wrong with her.
As for moving away and/or going dark. Yes those are options you have, however I would advise you to wait before making any big decisions like moving. There will be enough big rash changes coming from her, you need to minimize the damage for you and your son. Limiting contact with W is usually a good idea to minimize the hurt and damage from W.
Something you will hear a lot - this is a marathon not a sprint. Use the gift of time and dig deep for patients.
I understand the place you find yourself in. Keep the focus on you and son, and work on detachment.
Feelings are fleeting. Be better, not bitter. Love the person, forgive the sin.
