Welcome, Artist. I'm sorry for the tough stuff you're experiencing. I think you'll be very glad you found this forum.
I spent two years in a relationship with a high-functioning, well-respected, loved-by-most professional man in his late 40's. Sounds a lot like your guy. Even though we didn't live together, it became obvious pretty quickly that alcohol was a first love for him. After a year with a couple of painful break-ups in it, he also admitted a marijuana addiction, but he was "wanting change" and wanted me to be a part of his road to recovery.
I decided to be there for him, but quickly learned that 35 years of drug and alcohol dependence had a pretty tight grip on him. He was sober/clean for a few weeks and then we went right back to the same lifestyle/patterns.
Three months ago, I made the choice to walk away after the disrespect and the deceit became more than I could tolerate. My self-respect and dignity finally took over. It has been PAINFUL and enormously DIFFICULT. But once I realized and accepted that his real girlfriends were marijuana and alcohol, and that no amount of love I could give him could change that, it was easier to hang tough with my decision.
The only person I can control is me. My happiness does not depend on anyone but me and my relationship with God, my higher power.
I am also responsible for caring for my three daughters--they are my greatest gift and my greatest responsibility. It is up to me to be their example of a healthy adult who chooses healthy relationships.
Only you can decide what is best for you, but I think you are already coming to your own conclusion about that.
I honestly believe that if I had not stumbled upon this forum, I would have had an almost impossible time staying out of that very unhealthy relationship. I have learned here how addicts really DO lie and manipulate their way through relationships with WORDS as opposed to ACTIONS to hang on to the people who have become attached to them. It doesn't matter how much we love them. Their first loves are not their human relationships.
If you haven't yet, take time to read the stickies. They are loaded with eye-opening reality checks...things that will make you realize you are not alone...that addicts have common characteristics. Same script, different humans. We who love addicts have common characteristics. Same script, differnt humans.
I hope you stay and find the support and guidance you need here. Hugs to you.