Missy, my thoughts and prayers go out to you and your family. It is extremely hard to do what you are doing. I can tell you from my experience, as hard as it was, I was glad to do it. I didn't want to have any regrets that I wasn't there for my mom when she needed me most. She was always there for me, and now it was my turn to do the same.
My one brother, too, was trying to "save" her at the end. He was always asking the doctor if there was hope, even though she was being discharged to hospice care.
I was blessed to have a very supportive husband as well. There were many nights I wasn't home, and he took care of the 3 kids. He made things better for me.
Take this time with your mom, and talk to her. Cherish every moment, as I'm sure she is doing the same.
God bless.