My mom has developed dementia & her 88 yr old husband won’t give up POA. My brother is secondary who’s not involved. Any advice?

My mom(87) suffered a stroke which progressed into CHF, dementia, deafness & mild Parkinson. My stepdad (88 & POA) fought against assisted living but agreed only if he went one particular facility (badly rated) & didn’t provide medical needs my mom needed. My brother (reserve POA), supported stepdads decision, believing nothing should interfere w husbands wish’s. Since then the NP at facility overdosed my mom which led to hospitalization for 1wk monitored detox. At that time my stepdad & brother found a memory care facility which they had me go look at (a 2bedroom for them to move into), mom needing supervision & Dave needing light care. The place was nice & I said ok. The next day mom was upset in the hospital room after everyone left & I asked what was wrong? She was crying saying she just didn’t want to go somewhere she didn’t know anyone! I assured her I’d never let that happen. Next day they transferred her to the memory facility by herself & the husband never moved in. She was hysterical & devastated, screaming & crying not to leave her there alone. At one point she actually fell out of her wheelchair & broke her hip so upset. He moved into their retirement home & has almost bankrupt them now. My brother, living 5 min away visits possibly 4 times a mth for about 5 mins & her husband now visits about 1-2 times a Wk for 15 mins. The care is for mild patients & my mom is past this point. Currently she’s eating @ 500 calories from depression & will only eat if I take her out. My brother is a millionaire & I don’t have the money to fight him. How do I get control wo $$$$. TY