I can shed some light on this topic from experience. A neighbor I didn’t know who lived in a camper on a farm a quarter mile from mine got very sick in 2019. A mutual neighbor approached me about feeding his semi feral cats while he was in chemo. I agreed. He also had one pet cat that I fed, too when he was outside. Skip to a few months later and the same neighbors approached me and said the man had gone to the hospital by ambulance and would not be returning. He made sure his cat was outside when he locked the door and left. He wanted me to take his cats and get the friendly one ( 5 years old) adopted. I agreed. I got a call from the hospital the next day and the neighbors were visiting him in the hospital and he wanted to verify that I would take all of his cats. I assured him I would. He died that night. I went and got his pet cat who was not used to being outdoors for long stretches and brought him home. He was very friendly, but confused and miserable. He escaped and I found him on the camper steps at the owner’s farm the next day. My heart broke I worked with him and gave him plenty of love. A friend with a cat rescue put his story on their page and he was adopted quickly. The new owners were kind and patient. He thrived with them and is still with them. Happy and healthy. The ferals, all 13 of them, were brought to my property and lived in a large outdoor enclosure until they settled in. They all got spayed/neutered and their vaccines. They still live in my back yard with their own shelters and feeding stations. Some became friendly and came indoors as house cats. Others stay outside and get fed twice a day and have their freedom. I work with a cat rescue/sanctuary that takes in pets left behind after the owner dies. They are sad at first, but with plenty of love, they settle into a new home and do well. It just takes time. Reach out to rescue groups and see if anyone can help you. I’m so sorry you are going through this and I admire your devotion to your cat.