Hi Jim. Your situation sounds so frustrating and sad. I'm really sorry your mother has gone through such a terrible time, and I hope she will begin to recover soon.
Your reaction to your dad's behavior is probably pretty normal. You're under an extreme amount of stress, and I think we always tend to take that out on the people closest to us.
No matter how much you care for your students, you're more emotionally detached from them, so it's easier to be patient and understanding -- and you only see them for a certain amount of time, in certain situations. You get to go home at the end of the day and whatever they do, and however they behave, doesn't affect you after that. With your dad, his behavior affects you very much, even when you're not physically with him.
The most important thing is to remember, as you said, that his behavior is not him -- it's his diseases. After the earlier stages, people with Alzheimer's are in their own worlds and they're like children in the way they see everything and everyone around them. They can only see how it affects them. They're also like children in that, when they want something, they want it right away. That's not stubbornness or selfishness, and it's not deliberate. Your dad can't help thinking only of himself. Talking to him about it won't make any difference because he's probably not capable of understanding the concepts of empathy or patience.
From your father's perspective, what's going on now must be just awful. The most important thing in the life of an Alzheimer's patient is structure and familiarity. His life is turned completely upside down and it has to be scary and overwhelming for him. Living with your mom in their home, doing pretty much the same things every day was comfortable for him. Every single part of his life is unfamiliar right now. For an Alzheimer's patient, just going to a new grocery store can be very frightening and upsetting.
Your mom obviously isn't going to be able to care for your dad, at least for quite a while, so it may be time to think about bringing in someone to help. Your mother is going to have a hard enough time without worrying about your dad's care. She needs to be able to concentrate completely on getting through her chemo and getting better. She would probably tell you she can handle caring for your father, but please don't let her do it. You're seeing first-hand what the stress of that can do.
Before you go back home, I think it would be really helpful if you could talk to someone at the local Alzheimer's Association about the situation with your parents. These are things that they deal with all the time, and they should be able to provide you with invaluable support, advice and resources. Joining a support group at your hometown Alzheimer's Association could help immensely once you get back home. One of the worst things about having an Alzheimer's patient in the family is that you feel so alone and helpless. Hearing from, and talking to, people who are dealing with the same kinds of things can make all the difference in the world, both practically and emotionally.
You are far from a bad son. You're in the middle of a heartbreaking situation, and doing the best you possibly can. You seem very caring, and you're being a tremendous support to your parents.
I hope you will keep us posted about how things are going, and that your mother's condition will improve. My heart goes out to you.
Carol