End of life

My dad is 97 years old and is in Hospice at my house. He has copd, congestive heart. He is on 3 liters of oxygen 24/7. His blood oxygen will go from 82 to 95 in 5 minutes is this normal? I have been told by hospice that he is declining slowly. He is bot bed ridden yet and he still goes to the bathroom and showers on his own. He is getting weaker but he is stubborn and will not let anyone help him. What are some of the other things that I need to look for? I have been told that he probably will not make it till the end of the summer. Summer is gone and he is still here and I am happy for that. I work and I have a person their with him but I want to be there when him time ends and I am so worried that I won't be. If you can give me some helpful things to look for that will be good.