I screwed up a friendship big time and I really want to make amends and get him back in my life. How?

There could be some friendship genius's in the "Friends" category. Anyway--are you looking to get back in his good graces only because you have this crush on him? And if you disapprove of his lifestyle choices, why do you like him so much? You definately need to think about it all, then sit him down and explain all of your thoughts and feelings to him. His reaction will show you if he is a true friend.