A previous WAS is not going to joke about co-habiting unless thinking about reconciliation.
Why not meet with her before the Santa thing and see how it goes? (Not suggesting you move in, but if you have hopes of reconciling, at some point you will have to date. She's asking you out. She's initiating. She's interested.)
What is the problem with the Santa thing? (not saying that you should go, I'm just not sure what your concern is... If a private date feels good, why not Santa after?)
Finally, don't try to make your choices based on guesses about life in the future. Do what is right in the present.
