MLC - you had a number of questions that I didn't answer.
Yes, I could have taken an apartment myself, but expected the future to be like the past (commute from here, an hour away from d16 school, which is what she did last year). The changed living situation broadsided me.
Got it on the MIL front - thanks. My MIL is actually kinder and closer to me than my W!
Going to the West Coast for 2 months sounds good for the moment. I have subscribed to an apartment finding service already, which actively sends you notifications of new places that match your criteria.
No, I don't think she sees my staying in the house as better than her small place. She gets to be away from me, whom she can't stand being with (to quote).
Yes, fear drove me, wanting to hang on to the familiar, the comforting, the known. I guess I need to learn to let go.