As you are finally discovering, when someone is involved with drugs, they are not completely involved with you. There has always been an affair in this relationship — his affair with drugs. The good news is that he has admitted to an addiction problem. Apparently, the hospitalization was a wakeup call. The test of whether he is someone to stay with is whether he follows up with treatment. People can and do get into long-term recovery. People can and do give up drugs forever.
Your role in this is to cease being so tolerant! You absolutely should mind that he is using weed every day. You absolutely shouldn’t tolerate that he uses cocaine — even occasionally. It may not affect your life all that much now when you’re both in high school but it will definitely affect his ability to get on with adult life once you get out of school. Growing up means learning to manage emotions, decisions, social life, and relationships without the haze of drugs. He needs to find a better group of friends and much better things to do with his time that will help him prepare to get into adult life, not check out of it.
I suggest you find the local chapter of Alateen to help you figure out how best to be helpful and whether the signs are right that he is worth sticking around for. Alateen is part of the Al-Anon programs. It helps teens who are affected by someone else’s drug or alcohol use. Check out the Alateen website. You will find out more about the program and and you can locate a meeting near you.
I wish you well.