My mother who has dementia told me today that my dad yells at her all the time and pushes her down. I have seen bruises on her and when I confront my dad he says he's holding her so she can't beat him up. I know that she did punch him in the face and she does get very angry. She goes after my dad but then tells me he's mean to her and hurts her.
https://www.agingcare.com/articles/how-to-handle-alzheimers-disease-lying-144204.htm
Tammy, is your Dad your Mom's main caregiver? Caring for a spouse who has dementia at this phase can becoming physically and emotionally overwhelming for him. He might not say so.
Might be time to sit down with Dad and see what options does he have, as this must be very difficult on him seeing your Mom in this phase.
And like FF said, it is time to have that very difficult chat with dad about the care she needs and that he cannot safely, provide.