I would go with my gut feeling. It sounds like this would be way too much for a man his age, and yes, he will get sicker. Why allow him to go through that? That is an answer only you and your family can answer. As children, we never want our parents to die, but it happens, and we should think of them. My Mom died of lung cancer, and yes, chemo prolonged her life and that part of her life, she suffered terribly. If it were me, I would not do it. I would make my needs known, have the pain taken care of and go with dignity. Chemo at the end stages of cancer, removes the dignity and the quality of life. Pray about it. I will pray for you so that the right decision is made with much wisdom. God Bless You.