My father in law died a few months after his diagnosis, having had a fall. When he knew he had dementia he was terribly depressed and admitted feeling suicidal as he feared the future. Even in the period between early symptoms and his recent death, he was deteriorating rapidly. A highly intelligent man, he couldn't remember things, confused his words, didn't want to take medication and easily lost his temper and punched out (thankfully only at furniture). The future looked pretty bleak.
I have also worked as a Care Assistant (not a nurse) with people who had dementia. I've had to dodge punches and the things you describe, I have witnessed. However, I could clock off and go home to recover from the stress. A carer does not have this luxury. I take my hat off to you and send you a big hug
Can you get any help with care to allow you a break? Have you approached Age UK for advice? What about Social Services, GP, or the Consultant team who are managing your mother's case?
Please try to get someone to step in to give you a break and allow you some ME time.
Lots of hugs and warm wishes,