My moms memory is getting worse each day. Brother has abused her financially, mentally, verbally, and now physically. Advice?

I'm sorry your in this situation, what you have described is horrible. My advice would be to first find a place for mom or somehow get someone to help you at home because it sounds like her dementia is at a point where she needs 24 hour care. You will not be able to handle her by yourself anymore. Then, you are going to need to deal with your brother and the house. I would suggest consulting with someone in authority to best go about selling the house because I foresee your brother doing whatever he can to sabotage your plans up to and including destroying the home, rendering it worthless. His stability is being threatened and expect him to behave like a caged animal. I don't have the answer, but I would consult with legal authorities on how best to proceed and limit the damage. First though, you need to place your mom. You cannot handle her alone. Best wishes, keep us posted if you can.

Just because this happened does NOT mean that YOU have to be your mother's caregiver now. There could be difficulty with Medicaid eligibility, though, if she's been gifting your brother money over the past 5 (in most states) years.

Please don't sacrifice your own health and wellbeing over this.

This is awful. Please look into finding a suitable place for your mom.

Call a social worker if you need help in sorting everything out.

I’m glad you got your mother out of there. Sounds like her care has become more than anyone can handle in a home setting. Time to look into memory care or nursing care to provide for her needs. And consult with an elder care attorney to get help to see if evicting brother is possible so you can sell house to help pay for her care. The facility can help you apply for Medicaid when/if that time comes

DragonFly, does your brother take drugs or drink do you think? Is there something that "set him off" when you visited? Is this his norm?
In your intro to us you tell us that the brother lives with Mom but does nothing, but you tell us here that Mom cannot bathe or fix her meals, or even find her way to the bathroom. Mom getting worse? Is this sudden? Could she have a UTI?
Has brother been bathing her, getting her meals, dealing with her breaking things and screaming in the night? You have Mom with you now and are on 2-4 hours of sleep, and that must have been the case for brother in the home with her also?
Has the relationship between you and brother been once OK, but now everyone is completely at burned out? You say you are POA for mother and wish to sell her home. I wonder how you will be able to do that with your brother in the home? Will he allow it to be shown for sale?
Try to get together a list of things you must do now. If Mom's worsening symptoms are new, then see about a UTI check on her early this week. I would plan to see a Lawyer because it does look like you will have to serve papers on your brother preparatory to selling this home.
I know it is expensive, but as POA this can come out of your Mom's funds while she is with you, as it is about selling her home. You can also have a lawyer look over your POA paperwork to be sure it is secured and good enough to do a sale on her home. If not you might need guardianship.
I am so sorry you are going through this. Your Mom may require placement. Only you can be the judge of that. A call to EMT will get her transported to ER by Ambulance to be checked out, which she may need eventually and if that is the case, and you can find a good Social Worker, that would help.
You must be just in torment and I hope there is somewhere there SOME support for you, even if only friends.