Focus on getting through today and tomorrow. Conduct yourself with dignity and don't lash out even if you have the perfect opportunity. Now is the time to show your family how a man should act under circumstances such as this.
After Christmas, then think about the next step. I have a feeling that something is in the making. I don't buy that stuff about how she's all friendly b/c the other wasn't working. OM has said or done something to put her on cloud nine. I'd think a weekend together is coming up, so be prepared if she suddenly has some excuse for being gone overnight.
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!