Hi Mz,
Welcome to SR! You will find a ton of support here; I personally could not have gotten as far as I have without the support of the kindred spirits on here...so we hope you stick around, post, read, and learn.
In my experience, detaching is an ongoing thing, meaning that I have to work on it daily and put myself in "check" when I feel myself slipping back into the "comfortable" (although not necessarily healthy) ways of thinking. It feels awkward and wrong at first, because you care about the person, but you have to at some point for your own sanity and well-being.
We cannot control what others do, but we can control our reactions to their decisions and decide what is best for us and our family.
For me, with my alcoholic sister, I got to the point where it was no longer healthy for me to be around her self-destructive tendencies. I love her with all my heart and hope she will one day find her way back, but it's up to her to do that.
It sounds like you have a healthy concern for your son and yourself, and that's a good first step. Doing the "right" thing is not necessarily easy, but you will know it's right because it will feel right for YOU and YOUR situation.
Wishing you hugs.