I believe there are different types of Power of Attorney. I have one that is limited to medical care decisions for my grandson should he be hurt and his parents can't be reached. Make sure you have the right one.

The Alzheimers Association has lots of good information on how to care for and deal with your mother's dementia and can tell you where to find a lawyer who deals in problems like yours. I think you may need one. It's always good to know your options and to take the correct steps in the right order to make things work for you. A geriatric lawyer might smooth the way and help you to not do something you will regret later. Another thing the AA used to do, was provide a list of care givers who can come into your house for an hour or two to allow you a break once or twice a month. I'm not sure they still offer that, but it's worth a phone call.

I took care of my MIL for a few years until she became so bad that we had to put her in a nursing home.

My husband was an only child so there were no siblings to argue with, but her brother and sisters had a lot of thoughts on things. When she started getting bad, she was living 900 miles away, but in close proximity to her siblings. The one that was the most adamant that she stay put, we convinced to move in with her. That lasted less than a year and she cried uncle. And this was before she got really bad.

So tell you brother that since he wants to "help" by telling you how to do things, then he can have mom, regardless of whether his house is suitable. They can modify the house. Turn the living room into her bedroom, etc. Add a shower with a seat. I have lots of friends who have had to do all that to their houses to make them usable either for their older relatives or their own family members as they get older. The utter selfishness and unappreciativeness, (did I just make up a new word or just misspell it?), of some people is staggering. He shouldn't be questioning anything you do regarding cars, houses etc. unless he's willing to take on the other responsibilities. Of course you can approach him with more finesse than what I have said here, but when push comes to shove, these things are not his decisions unless he wants to take on the burden of care giving 24/7. When he's willing to do that, then he can have a vote. He can always suggest, but that's all he can do. You and your husband get final say. You need to make that clear to him.

And I agree with another suggestion, keep records of what you spend and whose money is buying it. Like I said, we didn't have to account to any siblings but since you do, you may need those receipts and records.

I know how hard this is and I wish you all well. Try to enjoy yours mom's lucid moments and try to find things that you can both laugh about. The worse my MIL's recent memory got, it seems the better her childhood memories got. When your mom is in a good mood and comfortable, ask her about her parents and what it was like when she was young. You may not get a response, but who knows, you might find out all sorts of things you never knew.