I think he has Schizophrenia.
That would explain him perfectly.
ADD-IT: I also had a frightening thought. Maybe I'm the only person left who still talks to him, and this is the way he talks to people he's friends with.
O_o
EDIT: I've finally blocked him on YouTube, and will update the Tumblr thing with the rest of our communications. You don't have to read it - he doesn't get any smarter.