I am so sorry you are having a difficult time today. It takes time for your brain and heart to come together and realize that there is nothing you can do to help him. This is not an easy journey for the mlcer or us. We are facing the pain and heartache head on w/o self-medicating, while they are out there playing the game of teenager life and dealing w/an entirely different pain from us.
Sometimes the ow does drop ideas in their lap as to what or what not to do w/their spouses and family units, but most of the time the mlcer will come up w/ideas on their own; and believe me they are doozies! Her insecurity is already kicking in if she's posting stuff on her Facebook page. Try to not read it because all it will do is upset you. For all we know she could be posting this stuff because she knows or thinks she knows that you are reading it...it's best not to go there.
Once the holidays are over, he will be right there on your door step wanting you to work on the divorce. If timetables are set in place, he will watch the calendar and clock to make sure you do what you said you will do at that time. He won't forget it. I would suggest that you allow him to do the work for the divorce as much as possible. He needs to face the consequences of his actions.
Don't apologize for feeling bad. We all have been there. Cry if you must, but once the spell is over, let it go.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.