I think some of the things on the list I suggested are a way for you to rediscover your call to adventure. Man who is walking the path of the hero's journey will act in loving, but clear and strong ways.
I'm also saying that it's easy to be stuck in Limbo on the DB boards gripped by fear, especially if your spouse is moving towards divorce.
Michelle Weiner Davis, if you read her closely, does prescribe actions like no contact, being unavailable, making ultimatums, speaking to a lawyer, etc. at a certain point in the relationship. She never says you shouldn't legally protect yourself.
It looks like you are at that point. Your wife is sleeping with another man, plans on pursuing a new life with him, has asked for a divorce and has opened a separate checking account. She may be in an endorphin induced fog, but, clearly, she's acting hostile. She's taking very deliberate steps. She may be getting encouragement and advice from her family.
Sure, be the best person you can be. Part of that is reclaiming your dignity. Part of that is setting boundaries. Part of that is being a strong man and father and being the adult in this situation. Part of that is ensuring you and your children are protected.
The bonus is, sometimes, that clear, strong stand turns your wife around. Maybe she'll wake up, maybe she won't.
