Have you contacted the Social Security administration directly and let them know she's taking his SS checks with zero accountability with where the money is going? It's not legal for her to spend that money on herself. It's supposed to be going for your husband's expenses.

Have you considered contacting the local news media to report you and your husband are the victims of financial elder abuse and fraud with your stepdaughter pulling shenanigans behind your and your husband's backs with the POA to steal your money, your house, and to prevent you and your husband from ever being able to see each other in person again. A lot of tv news stations have those consumer protection and fraud cases reporters who focus on financial fraud of all types.

Are there other family members on your husband's side you can contact and let them know what she is up to, who may read her the riot act?