F--k. That's the first word that comes to mind. NM, I hate this. I hate seeing you suffer but you know what? This outcome, HIM actually stepping up and making a decision in a way gives you all the personal satisfaction (strange choice of words I know but I don't know another) that you tried all you could. YOU didn't give up on this when there was still something not to give up on, and I suspect you understand that this is not necessarily the end, even if in your heart it is. I don't say that to sugar coat anything, just to remind you once again, that at the very least, he's likely to flip on YOU again, even if you don't with him.
I have been thinking a lot about how it would feel if things got to that point in my sitch and I am like you, I can make myself feel ok about it for a bit, but in the end NM, I fully understand your sense of failure. Of course, I don't believe you ARE a failure but I can understand that after all these months, really YEARS of trying, it has to be so hard to just have it end.
NM, please don't be a stranger. Please let us know how things are going. Vent, cry, celebrate, whatever. I've come to know you as such a wonderful, powerful, strong, passionate, caring, loving, peaceful woman and I don't want to lose you to the part of your life that maybe doesn't include "us" anymore.
Just check in, and maybe someday that a$$hole (pardon me) will realize once and for all that he made the biggest mistake of his life letting you go.