I honestly don't think that you can care for a friend too much. You can worry about them too much, but there is a difference between the two things.
Anyway, unhelpful as it is, I think you are right in saying that do need to find some way to stop worrying about him and realise that he is responsible for his own actions. I'm not quite sure how to do that though??
Can you talk to this guy? That's what I'd do if I were you, sit down, have a proper talk with him, tell him that his behaviour is concerning you, and try to find out what the underlying cause of the behaviour may actually be? Just drinking too much? Attention seeking? Just being silly?
Point out how dangerous and unproductive his behaviour is, and try to encourage him to be more sensible. Maybe you could get another friend to back you up with this conversation if you don't want to do it alone, but whatever you do DON'T make it look like you are ganging up on him... Just remember you can't get across your concerns without communicating with this guy.
Hope this maybe of some help. Good luck.