Man, I can relate to what you wrote. I remember feeling all of those things... .all of the confusion, hurt, loneliness, and wanting nothing more in life than to help her... .
I'm truly sorry that you are going through it all.
One of the main things that I learned was that the best thing that I could do for myself, her, and the relationship was to stop rescuing. It was hard. Seeing her struggle killed me. But, I learned that I had to do it.
When we try to "rescue" someone else and solve their problems for them, they learn to take advantage of us and treat us poorly. They lose respect and we become doormats. We get used.
Because I had to learn to stop trying to be a white knight, I know how difficult and scary it is when faced with the change. As I said earlier though, it was best for all involved and gave the relationship the best chance for success.