Hello again @NorthwestJen . Thank you for the update, although your situation does sound pretty terrible for you to have to deal with.
I hope they are making your Nan as comfortable as possible , and with palliative care, they should be able manage the pain.. but you say she's in a lot of pain. I would speak to the manager to see if anything else can be given to reduce the pain. Stage 4 cancer - not nice. My own Dad went through it and it's just horrible to see your loved one like it. I hope when the time comes, it is peaceful.
It does sound like your Grandad is all over the place and is obviously missing your Nan. If she really doesn't want to see him , then that should be honoured I guess. When she does pass, I think you need to tell him, and it will be awful and upset perhaps for a while, but by what you say, he will probably forget.
You have so much going on at the moment with it all. I don't know if anything I've said helps, but just know that we are here on this forum, we do understand, and want to help.
Wishing you strength ((((virtual hugs))))