Get a sign, like Lucy in Peanuts had, "Psychiatric Advice, 5¢" and tease them about asking you to define the world just because you're a captive audience. Sounds like your friends really enjoy you and think highly of your advice. They're not just asking for help from you to be nice like you think they're asking you to play for. You're a magnet to them for some reason, use that if you can to help them.

Tell Mike it's a new day and if he gives you drugs one more time, you're telling his cousins and that he's not allowed to talk about his substance abuse and clubbing with you anymore either, you're trying to give that stuff up. Mike cares about you if you all are that close, admires you probably and what you're trying to do with your life, etc. You could be a big help in his life if you keep moving forward with your own like you are!