I think that unless/until the Dad admits that he has a problem, it is unlikely that the boy will also admit that he has a problem. Sadly, forcing someone into treatment when they are not ready and willing does not work. They can sit there, even participate, but they won't change what they do when they are released.
Forcing your son to live with you will only make him hate you. It puts Dad in the place of "Good Dad" and you in the place of "Witch Mom" and that will be how you are seen forever. I think you have to let him live with Dad and ask him to spend time with you doing fun stuff. Make a concerted effort to do things with him that he considers fun even if you really don't like them - but don't let him see that you don't like them. Work to make positive memories with him and to connect with him. Maybe he can live with Dad but he has to spend so many evenings a month with you. On those evenings take him out to dinner or to a movie or to do whatever HE enjoys doing. I know this sounds strange. It will change how he sees you and help rebuild your relationship.
I do think that the substance abuse and drinking must be addressed, but you and Dad must be on the same page or Dad will just undermine everything you try to do and all efforts will be useless. I think you need to speak to a substance abuse counselor and attend NA or AlAnon meetings to see how YOU can change for the better. You have an ex with a problem with alcohol and a child with a problem with drugs and alcohol. Clearly your life has been negatively impacted by drugs and alcohol, so meetings could be helpful for you. Going to a few meetings to see what they are about might really help you see what an impact addiction has had on your life (even if you don't drink or rarely drink!) and how you can change this. Many people don't realize that even if you are the grandchild of an alcoholic you learn behavior patterns that are unhealthy that are due to the messed up ways of thinking of the alcoholic. Changing this has a huge and beneficial impact on your life. I know, I am the granchild of an alcoholic. I am also the sister of one.