Jeff, just had a chance to read this thread. I am so sorry to hear what your mother and family are going through. Not a part of life any of us look forward to.
My wife lost her father to brain cancer six months after we got married. Had you not known his situation you would not have known he was sick until the last four weeks, then it took him fast. Very hard to watch. He did radiation to shrink the tumor to try and keep lucid as long as possible but refused chemo as he knew how it can affect your quality of life. My wife and her mother, a retired nurse, took care of him until his passing.
Five years later we packed up all our stuff, put them in storage, rented our house and moved in with her mother to help her as she was dealing with emphysema. Emphysema is a terrible way to exit this world. A long slow suffocation. I didn't want to move in but she begged us for a year before we finally did. Mostly due to my wife's older brother who was making her mothers life even more miserable. We didn't really understand what we were getting ourselves into. I was working seven days a week keeping my young business alive and my wife was raising a one year old and caring for her mother. She passed two years later, three months before our second child was born. It was one of the most stressful times of our lives but we have no regrets.
I lost my mother unexpectantly five years ago one month short of her 82nd birthday. She had a heart condition but seemed to be managing it well with medication, was active and full of life. I had an unusually long and wonderful conversation with her a few days before. She passed quietly one evening while reading her bible. Her mother had dementia and she had always been terrified it would happen to her. While we miss her dearly I take comfort that she did not suffer.
Now my grandfather on my dads side had a hard life, worked everyday of his life from the time he was a child, had a fox farm, ran cattle, grew potatoes, beans and hay, was the county water master and owned a tavern in a mostly Mormon community. Outlived my grandmother and a second wife. He didn't drink but his third wife was a professional chain smoker so he might have well been a smoker himself. Ate all the wrong things and didn't take the greatest of care of himself. In his 92nd year, half blind but still driving a ratty 30 year old Datsun pickup, came home one day and announced to his wife that he had sold the tavern and the acreage, set her up a trust and said he was done. He passed three weeks later napping in his recliner. My hero.
We miss those we have lost but are grateful for the time we had together.
I hope the best for your mother, you and your family.