You need to take your mom to a doctor who specializes in Alzheimer's disease - if you haven't already. Call the local Alzheimer's Association and they will refer you. She is having some usual symptoms and your father may or may not be doing physical harm to her, it is hard to say. He definitely needs a break from her care - he cannot think properly right now. You are telling him the right things, do not argue with her, but for some reason, he cannot stop himself from doing that. He really needs a break.
It is possible that she needs her meds changed and in the hospital they may be able to get her regulated.
Call the local chapter of the Alzheimer's association, they may have someone who can help you. Or call the Area Agency on Aging and they will help you.
Most of all, find someone who can help. Your family is in crisis and you all need help.
This is a horrible and difficult time, but help is available. You can find almost everything I referred to above on the internet.
www.alz.org
Get on the internet, call, get some help!
I'm so sorry this is happening.