Valerie, welcome. I don't know if there's an easy answer as to how you can convince him that rad and chemo will be rough; I guarantee he will discover exactly how rough they are all on his own.
He won't likely feel too many bad effects for the first couple of weeks, but when things start to turn, he will be sick; much sicker than after surgery in all likelyhood. Sense of taste will go away, mucositis and thick mucous will begin, he will be incraeasingly tired, nauseated and lose interest in eating or drinking.
He will be, in all likelyhood, a very sick guy, and it will last for some weeks, even after treatment ends. I can tell you from personal experience that it will not be something he can ignore, nor do much about. He will need your help on an increasing basis.
I had 17 hours of surgery, followed by a heart attack during the first 24 hours after I left the operating room. Comparitively speaking, if I had to do anything over again and could pick between the surgery or another round of radiaiton, I wouldn't hesitate for a second; the surgery was the easy part of the treatment.
I wish you both much luck. He has a tough battle still to fight, and he will need a lot of help from you
Wayne