Sanderika, the reason this behaviour is so familiar is that my h also did this. It was more dramatic with him, because in between times he was very mean. But I decided to put a stop to it last June, backslid a couple of times [to the extent of exchanging texts, but have been totally without contact since our divorce a few months back.
And you know, I feel so much better. I am finally starting to be really OK. We get locked in to their drama. Everything you say is true. We can never know whether our actions are enabling, prolonging, or helping them. The point is that it has to be about what is best for us, after all this time.
I believe that if and when they "get it", they get it, and until then there isn't a lot we can do except protect ourselves.