For sleep have they given you Ambien? Some doctors don't like to prescribe it because it's very addictive, but I am a chronic insomniac and have found it effective. It can't be used for more than 30 days though.
As far as your biological mother, the exact same thing is happening now with my mother. She is 85, has lung cancer and then broke her hip and had an emergency surgery in April. Since then she has been unable to get out of bed, unable to rehab her hip, unable to resume cancer treatment (which had been effective), and although she isn't in pain her quality of life is zero. So she has stopped eating, has lost a ton of weight, and although I don't sense depression she is resigned to death and mostly is just talking about what she wants to happen upon her death. All of this has taken a tremendous emotional toll on my father, who is healthy and visiting her daily apart from a couple of shutdowns due to nurses contracting Covid. But it's now basically a Hospice situation with my mother, and because she and Dad are in Florida, it's not feasible for me to visit and my father has forbade me from even thinking about it. So I can completely relate to what you are saying on that.