I'm so sorry to hear about your Dad. I think the side effects for everyone is different, but Tommy has handled the chemo very well. He is a little more tired than normal for a few days after each treatment and occasionally has a sore in his mouth (but that is easily treated with a prescription mouthwash). The biggest problem he's has is neuropathy (numbness and tingling in his fingers and toes and being very sensitive to cold foods), but that usually only lasts a few days after each treatment. He feels it's worth these few side effects for the benefits he's received from the treatment.
I haven't heard of the Naltrexone, but let us know how that goes. I'll keep your father and all your family in my prayers that this helps him.
Cindy