I think Alzheimer’s is complicated by having a body, though. My grandma had it and was happy, not angry. It sucked for us and for her because she eventually forgot how to eat & take care of herself at all. To have that lack of understanding of reality doesn’t seem nearly as bad if you are a disembodied consciousness, as this suggests. It seems more like a death than the other choices.

Alternate Dimension I would go for only if it was a gamble not a certain “being torn to shreds by demons over and over” situation.