Well, two books that I've read on co-dependency are by Melodie Beatty and they're entitled Co-Dependent No More and Beyond Co-Dependence.
And good for you for considering what your problem might be rather focusing on what his problem is.
It's just my opinion, but I think we all need to be needed. We just need to know where to draw the line.
I know I delivered one helluva narcissistic injury when I left the n. And it hurt my heart to see him suffering. But I had to save my own life. And he will survive.
Better that I work on myself (and you do the same) than to "hang in there," hoping for a miracle that will probably never happen.
They are manipulators, and they will manipulate their way through life just fine. I put 1000 miles between me and the n. I won't be running into him in the grocery store. And when the phone rings, I ignore it. I feel better every day.
GN