I've only read the OP's updates, but - - - is it possible there's another woman? I had this with my now ExH. My works Christmas dinner, he pointedly sat next to other people way over the other side of the table from me, ignored me for all of the evening, went to bed early at the hotel. When I went to bed he was texting on his phone ...
We went out for lunch with a large group of friends - again, pointedly sat away from me, went out to "the loo" for about 15 minutes -
MIL over Christmas and he walked the dog at the same time, was gone for ages. I said one morning we'd join him, his face changed, he disappeared into the park's cafe loo's for 10 minutes (MIL asking if he had an upset stomach, you could feel the waves of anger coming off him).
NYE, out with a large group of friends to see the fireworks in London, as the bells chimed we all hugged each other, he body swerved me and as it quietened down said loudly "I didn't even get a kiss", scowling at me ... Reflecting back afterwards I should have said "Neither Did I"!
When, 6 weeks later, I saw his mobile phone bill with all the calls to the OW, it made sense. At the time I thought I was going a little crazy. Yes, it took me that long to figure it out ....
It's the time of the year when this stuff happens, there'll be more in the next 2 weeks. You're with each other more over Christmas, the OW (occasionally) is someone they work with, etc ....