Hello Katrina:
Count me in the "mothers who can love their adult children to death" group. I have more than one adult children who are extremely dysfunctional/drug addicts. I am so sorry you are going through this, but as you can see from all the postings, you are not alone.
You have done little to nothing that we all have not done and sometimes still do. I keep dusting myself off every time I contribute to their downward spiral and emmerse myself in reading and concentrating on me. Serenity prayer will usually break my obsessive thoughts about what I can do to stop them from self-destruction. I'm not where I want to be yet, but I am slowly climbing out of my hole.
My prayers are with you and your family. I know this is difficult, but read all the postings with an open mind. What have you got to lose but the insanity?
Huggs