Rachel,
Your story is very similar to mine. I will not offer sage advice as I am very very early in my own recovery - in fact I screwed up so badly this weekend I'd assume I just start over tomorrow morning!
You are not alone. Dreams are hard to let go of, especially when your dreams involve another person.
All I can speak of is my experience. I was with my boyfriend for 2 years although he spent 5 months of that time not returning my phone calls and 3 out of the 5 months with someone else. He was a beautiful person when he was sober and i just couldn't give up on him, couldn't give up on us, couldn't give up period.
After two years, after he missed my grandmother's funeral because he was high - I finally had had enough. I called him and asked him to be silent and listen with his heart, not his sick, cloudy head. I read him a letter I had prepared explaining that his addiction was painful to watch, painful to be a part of and that I would no longer help him or watch him kill himself slowly. (I'm Italian and quite the talker so the letter was much longer than that - but there's your summary)
The next morning I received a call from a nurse at a detox center stating that he had checked himself in that morning and had asked her to call to let me know where he was and that he was safe.
IN MY EXPERIENCE (that is all i can speak to), when I had finally had enough---that's when he decided that perhaps he had had enough too.
But he had to make that choice for himself.
And only YOU will know when You have had enough.
I used to think that Love conquers all...but if he's an addict he doesn't love himself. And the most loving thing you can do is put a spotlight on the situation - "I love you - And I love you TOO much to sit by and watch you slowly take your own life"
Much easier said then done i know. And mine had the best possible outcome - some do not.
Please just know that you are not alone - and you don't need to " go down with the ship"