My stepdad does not want to be with my mom anymore because "he has his own life to live". He is threating to put her in a home so he can "live his own life". She still has all of her facilities. He is extremely abusive to her and is trying to make her dementia advance faster by the abuse he gives her. She does not want to go in a home. She wants to stay in her own home. Does she have any rights?
Does your mother need a higher level of care than her husband slone can provide? Are there other caregivers coming into the home to care for her so yhat he can visit friends, go grocery shopping, get some down time?
Have a needs assessment done by the local Area Agency on Aging. Don't take your mother's word for the fact yhat she can do things like bathe or manage medications. Find out what her needs on and then figure out, with her husband, how those needs can be met.