My mother is neglecting my father.

Hello,
My parents are 82yrs old & living in their home in Georgia. My mother is bedbound with several co-morbidities including memory loss . Yet , she is the most manipulative, evil person on earth. My father has stage 4 Parkinson’s . He is competent at times but sometimes has confusion & hallucinations . They made me , their only child, their POA decades ago but my mother does not want me involved in their affairs. My father has always managed their affairs . He asked me to take over their financial affairs several years ago which I have done successfully. He also made me his Health care agent because he did not trust his wife to make the best decisions. This made her angrier & vindictive towards both of us. They desire to remain in home & pay for private nurses and at this time they can afford to do so. The problem is….. she tells the nurses NOT to check on my father and feeds them lies. I have a security camera in my father’s room and I’ve noted nights where no one checked on him. Over the years , she has paid nurses to steal his mail & credit cards. Unfortunately I don’t have hard proof but I’ve received various reports from other nurses . She would fire nurses if she couldn’t control them. I had to hire his own private nurse to stay with him during day. My mother claimed to have hired a night nurse for both of them but she demands that nurse stay by her side the entire shift. She has never showed any concern for my dad. I’ve called APS but she fooled them with her sweet lies. They saw the nice house & private nurses & figured everything was fine. I’m now in a position to care for my father , with help, in my own home. However , my mom threatens to sue me . When I kept him for a weekend ,she called the police and said I kidnapped him! She is only interested in controlling the money . I’ve wanted to petition for guardianship but I feel like she will pass the Cognitive test , and deny any of her wrongdoing. How can I free my dad from his evil wife?