I think what's missing in the story you tell is a genuine sense of commitment. I don't blame you for being with him since the age of 14; we all make our decisions and then have to live with the consequences. But I would ask you to consider whether the adjectives you use are really just ways of avoiding the conclusion that your relationship, as it now stands, is pretty dysfunctional and not in your best interests.
For example, what is "open and honest" about a relationship in which you live separate sex lives? To me that sounds more like "indifferent and irresponsible", especially if - as I suspect - it's a game plan he confronts you with as a matter of "take it or leave it", as opposed to a subject you two sat down and talked about and came to this decision.
The same with hard drugs. As a former user I can tell you for sure that no woman should be under any illusion as to which is more important - his habit or his relationship.
No one is trying to lecture you here, but the reality is that if you allow him to grab you into the abyss with him, that's what he will do. Not because he's a bad guy. But because a guy in shit as deep as what he's in will avoid the hard decisions until he absolutely has to face them. And also because he has a very immature and self-centered vision of what a relationship is all about.
At the end of the day, girl, if you are prepared to accept all this then you are essentially signalling to him that your feelings and needs don't matter. Not now, and not ever.
Nobody living can ever stop me
As I go walking my freedom highway.
Nobody living can make me turn back:
This land was made for you and me. (Woody Guthrie)