Welcome Newreality and I can't tell you how sorry I am for the reasons that brought you here.
I like what Troubledone said here >>> "What I discovered is that the guidelines that we hear about in 12 step programs for codependents are as hard to implement as it is for the drug addict to stop drugs. "
As you are finding out, it is indeed dingdangdadblasted difficult to enforce boundaries even when you know it is the best thing. I remember feeling like I was performing open-heart surgery on myself without anasthesia.
There are plenty of success stories of recovery for both the user and the codependent. Unfortunately there are fewer success stories of relationships making it but there are a few. Of course those in the relationships that weather the first years of the storm live constantly with the knowledge that a relapse can happen at any time.
I did successfully get out of my relationship with my meth addicted XBF. In the year following, he spiraled all the way down to dealing drugs and a long stint in jail. He did get sober and has remained sober for over 20 years as far as I know. I see him as very much of a success story and he told me years ago that I did the right thing when I left him.
I hope we do not overwhelm you. Finally a big, big hug to you as you face this very difficult situation.