First off, I love that you included the Samantha Jones quote at the end. My kind of lady!
I was exactly where you are 3 months ago. It is so difficult to end things period, but to end things when you still love (or are in love) with someone is even more painful...but here's the good news-it gets better. I can say that I am genuinely happy 90% of the time and that's because I walked away after another relapse. You can read some of my old posts/threads for the whole story.
I promise it gets easier. Stay strong, work on yourself, stay busy.
Hugs.