Namaste and Welcome to the forum.
It is commendable that you are concerned about the health and lifestyle of your friend and I think he should count himslef lucky for having a freind like you.
Yoga will and can help your friend, however, your friend needs to make the chnage in his mind and heart himself to want to change the way he is living. No matter how hard or how much you try to bring yoga into his life, if he hasn’t made the change within, nothing you’ll do will have long term effects.
Please also note that yoga is not a quick solution for all his problems. For example, yoga won’t change his eating habits, that he needs to change himself. He needs to make a commistment towards himself to take better care of his body and soul as well. Once he has done that, then only can yoga be the effective system it is meant to be in a person’s life.
Your friend has many health related problems and it seems also that they are severe, which might not be best addressed in a general mixed yoga class. Your friend will need more individual sessions with a competent and compassionate teacher. This might be expensive and again is your freind prepared to invest this kind of time, effort and money in his future health? In other words has he made the decision for himself? He seems to have made up his mind about things in life already, his “I can’t do that” attitude is more telling about how he feels about his life in general and I am afraid at his age it might be difficult to change that.
Good luck with your friend.