Prepare for angry words (that he means at the time, but doesn't really mean...if that makes sense). In his frame of mind, using drugs, he is not the same person he used to be. You are right in my opinion to choose the rest of the family, including yourself, over him. You can't fix him. You can spend the rest of your life trying (some people do), but he is the only one that can fix himself. It is really out of your hands, but you can still have a good life with the rest of your family.
And some of our kids do see the light...but THEY have to see the light. We can't show it to them until they are ready to see it.
Hugs.