Badger -- I feel for you. Difficult parents are hard to deal with. Let me offer a different perspective. In doing so, I don't intend to excuse bad behavior, but just to offer a hypothesis to understand it and perhaps allow you to let it "roll off" without feeling battered from it. I think in some thread in this forum someone wrote that you cannot control how people act, only how you do (and feel).
From reading the thread, I understood your mother is Japanese and your father perhaps was not. If I was to make sense of her behavior, I would interpret it as being scared, afraid of the future. The Japanese culture is fairly closed and hierarchical. In particular, elders are held in very high respect, their opinion consulted frequently. Your mother did something unusual - to move abroad and perhaps marry a non Japanese (ever asked her about her life story, her family's reaction?). Her sense of loss right now might go deeper than the loss of your father. She might view you as the daughter she has kind of lost: you do not defer to her, do not seek her opinion. As she's considering moving back to Japan, she might feel terribly lonely and about to go back to an environment where she might be viewed as a failure. She simply sounds not emotionally equipped to process these developments in her life.
PS: "old person car"? My reaction would have been: yeah. I'm old enough for it!

