Re: Problem student!!
Try talking to the folk in his other schools. Sounds like he might just have disability issues that prevent him from learning. Does he hold down a job, have a family, go to school, etc?
All you can really do is train with him as cleanly and safely as possible. Many of us train is aikido as a self-defense. How unhinged and difficult is someone who is actually attacking you going to be? Barring intentional cruelty from him, he might just be really good practice, if not a good training partner.