Karrie,
Welcome to SR. You do not sound at all out of line for the feelings you are having, for wanting to shut the door on your son, his addiction and all the troubles that go along with it. I understand (and I'm sure many others do as well) the feeling. You are not alone.
I know my attendance at AlAnon and NarAnon really saved my life, helped me to meet some amazing people and has given me tools to remain sane.
I don't have a "will" per se, but have changed my beneficiary to 60% to my daughter and 40% to my (now sober) son. During his years of using I had even changed it to 100% to my daughter. As time goes on and maybe he begins to take more responsibility for living an independent life I may change it to 50/50. But for now that's not the case. He still has a ways to go.