My father who is mentally unstable (undiagnosed) got medical power of attorney over my mother after her dementia diagnosis

I am wondering if anyone has any advice on how to get a medical power of attorney revoked. My mother was diagnosed with dementia two years ago and with it had her only form of state ID revoked because it was her driver's license. My father is a narcissist and has been mentally unstable, paranoid, and generally abusive lately. He is the primary caregiver during the day because I work full time but I care for them before and after work and on the weekends as I live with them. My father has made caring for my mother extremely challenging with his mood swings. Lately, I have been concerned for her safety as he will make unsound medical decisions such as firing her doctors and asking nurses to not check her blood sugar or give her her diabetes medications when she has been hospitalized. He was able to get a medical power of attorney over her in February of this year even though she has dementia and legally cannot sign anything, not to mention the lack of an ID. I am wondering if anyone knows how I could get this revoked without spending thousands on a lawyer. We are very low income. Or if anyone has advice on how to navigate the situation in general.