It's impossible to help someone who doesn't want to help themselves.
That said, it also takes time until we ourselves are ready to admit that to ourselves.
In my relationship with XABF (ex alcoholic boyfriend), I did not move on until I felt that I had tried everything I was capable of doing in an attempt to help him.
I ended up in debt, depressed, and emotionally/verbally abused, at the minimum.
In the process, I learned of what a strong person I am.
I also made sure that I could leave with no regrets.
I answered my own "what ifs," and that's what it took for me to be done.
You need to do what you feel you need to do, and then you need to let go, give up the notion that you have some semblance of control over his choices, and give him over to live his own life, unhindered and uninfluenced by our need to decide for them.
He will fall, yes, but it's the only way he will have a chance to pick himself up again.
And until they pick themselves up again, they cannot take responsibility for his own actions and decisions, and they cannot do what they need to do to stay clear of their addiction.
You are in the right place.