I know it seems tough to act happy and positive given your situation. It will get easier. Once you have taken care of your boys I would really recommend getting out of the house and doing things. Start a new sport or hobby if you can. It will help you to take your mind off your W.
Like LH said I think it’s time to stop playing family. She doesn’t want to be M any more and so you shouldn’t let her indulge in family time. Treat her with kindness but try to get to a place where you don’t worry about her thoughts or actions.