Dude, you know how to proceed. You're on the right track. You have just proven that boundaries work. Don't be afraid to tell her what you won't put up with. I made the mistake of being afraid of hurting my wife's feelings and here I am, still.
Everyone has been telling you what to do and what works. The FB thing may be no big deal. On the other hand, it is important enough to you to make you shake. Don't get all melty and think this is over. Stand up for yourself and stand up to her behavior that is threatening your M.
