Hi Bambi, welcome to the board, I'm glad you found us. I'm sorry you are going through all of this with your son. I too have an adult daughter who cannot take care of herself well, is sometimes homeless, makes bad choices, etc. however, it's mental illness, not addiction. I too am raising her daughter, my granddaughter, who is 16 now (and also thinks of her mother in a similar way as your granddaughter thinks of her Dad).
It sounds to me as if you have done a lot for your son, likely way beyond a lot. At this point, there is nothing more to do. I can say that with the absolute full knowledge of what that means to you and how much it hurts to get to that point. There is no where to go from here but for you to let go, detach, accept the situation and your son for what it is and who he is. You cannot change it. You didn't create it. You cannot make him healthy or guide him to the right place when he doesn't want to go there. Like you, I tried everything too. Most of us here do. And, most of us get to the point you're at, we hit that wall and then what? All your instincts say, protect, love, take care of, give, make better, help........but you've done all of that, right? And, he is still the same.
So, now is the challenging part, you must set strict boundaries, boundaries that have you as the focus, that protect you, your husband and your granddaughter, boundaries that keep your son's lifestyle choices out of your life. Which, I know from experience, is the hardest thing you'll ever do. And, at this point, exactly what you have to do. All you can control is your reactions to him and exactly what you are willing to do and not willing to do. I would give that a lot of thought and come up with a plan.
What I did with my daughter was to get her connected to the local Mental health organization which can provide housing, counseling, jobs, training, education, health care, etc. (NAMI- the National Alliance on Mental Illness, which you can Google and find a chapter in your area if that feels right to you) I paid for her to get to what I called "level ground" since she had, by her own choices and by some terrible things that happened to her that weren't her choice, fallen so far down, she needed some help getting back. I provided that help all the while telling her that once everything was arranged, she was then on her own. And, finally, once I accomplished that, I realized the other part of her life is creating intense dramas which were emotionally, physically, mentally, financially and spiritually draining me, so I told her to keep all of that away from me because it was having such a negative impact on me. The final boundary I set with her was to tell her not to contact me until she had gotten into therapy AND gotten a job. I cannot be involved in her life. So far, she has honored that request. I have no contact with her except occasional emails. I hope she can avail herself to the help that's been offered, but I don't know if she will.
This is not the ideal life I wanted with my only child, but it is the only life I can have which respects me, keeps me out of the insanity of her choices, and keeps me away from watching her live in the horror of her life where I feel helpless, angry, filled with sorrow all the time and hooked into riding the line of helping versus enabling. It is just too much for me. I had to let go and I had to accept my limitations in what I actually could control in her life, which is nothing.
Your son, like my daughter, may end up living on the street, go to jail, get hurt, or worse, on and on the scary thoughts will go............and there is nothing we can do. I am in your age bracket and since I let go of my daughter, my life is reflecting calm and peace and laughter once again. You deserve that, your husband and granddaughter deserve that too. And, soon, she will be off in her own life and you deserve to retire and enjoy your life NOW, not when you are 90 and your son is still stealing your life force from you.
Get support to do this, it's very hard. Get into therapy, get into a group. talk more here, read books, pray, take long walks, appreciate nature and laugh more. For me, getting a lot of support was the answer, it so helped me to make sense of all of this and to make choices for ME. Our kids are in G-d's hands now, a far better place then ours. I'm sorry. I wish you peace and the knowledge that you're doing the right thing. (((HUGS)))