What to do about neighbor who harasses me, sometimes seems to be stalking me, and is just plain scary?

Go immediatly and get a restraining order against this certified lunatic. And i'm not sure i read correctly but did you say he lived in the same apartment complex? If so, as many complaints you have had against him, the landlord has every right to make him move Out. It's either you move or make him while in the process of getting a restraining order against him. Don't put anything past this guy who has obvious serious mental issues.