I think a Christmas gift or not is not really a priority right now. In light of your current situation, unless failing to give her tokens of affection was a problem area, it doesn't make much sense to me. How about a simple Christmas card saying "Merry Christmas" if you feel you must do something?
I was glad to see your post about your OWN issues. With all the many things you mentioned in other posts, what stood out to me was that you probably were not the easiest person to live with, and probably an even more difficult person to stay madly in love with.
I don't say that to be harsh, but to agree with you that YOU have work to do on YOU, and this marriage crisis is one that BOTH of you made.
Hopefully this will allow you to find some empathy for her current state. Infidelity is never justified however, so don't go overboard.
A stalemate never lasts, though they can seem to drag on forever. If you can stay the course, stay true to yourself, work on YOUR issues, and keep the relationship discussions to an absolute minimum, at some point SHE will break the stalemate.
I know you don't want the status quo, but neither does she. And nothing you do is going to force her into a decision, even if you ask her to make one.
Make peace in the home. Make the environment one that stays good for the children - it is the two of you who have the issues after all.
Fianlly, if you TRULY fear that she might up and leave with the kids and the bank account, do not hesitate to establish some legal protection. But don't do this just to punish her. You do it because you honestly are afraid that she might decide to clean you out and take off with the kids. I cannot tell from your posts if this is a legitimate fear or a wild thought on your part.
Blessings,
Bill
"Don't tell me the sky is the limit when there are footprints on the moon."