Does your friend know that you're writing about him like this on a global forum?

If he doesn't I think it's disgusting. You've mentioned very vague symptoms:

hey he's clumsy - lots of us are
his musical timing ain't great - most people's isn't
he likes people to play along with his singing - many do

I really don't thin you should start trying to diagnose a 'syndrome' from internet chitcat

John