My dad passed about 3 months ago after long fights with broken hips, dementia, heart problems, etc. We were lucky, as he went from being pretty good to being dead in about 2 weeks, and we didn't have to face the types of issues you're going through. The toughest thing was getting the call from the nursing home that we had suddenly gone from being fine to being at end of life. They had taken him off antibiotics and instead gave him morphine, and I flipped out on them for doing that. I wanted to give him every chance in the world to fight back, but in the end he died two days later even with the resumption of antibiotics.
When it's time, the person knows and you shouldn't try to change the course of nature.
