What "power" do I have as health care POA?

You can make medical decisions independent of him and as the financial POA, he must manage your mother's finances to pay for it. What is TCU?

Can your mother handle your telling her about what your brother is doing? Is your mother competent to change who is the financial POA?

TCU = Transitional care unit. mom has been in the hospital and decisions need to be made about : should she go back to AL and recv hospice care.. or go to TCU and get physical therapy.? TCU is paid for by medicaire - except since mom has mersa, there is $20/ night for private room. He would have to pay for that.. or can he refuse if I leave him out of discussion of where mom should go? mother doesn't want to cause rift by changing POA. she doesnt' believe bro is a problem

As Medical POA, you have authority to make medical decisions. And, no, Brother cannot refuse to pay if he doesn't agree with decisions. If I were you, I think I'd simply stop trying to talk to him about medical decisions.

TCU = Transitional care unit. mom has been in the hospital and decisions need to be made about : should she go back to AL and recv hospice care.. or go to TCU and get physical therapy.? TCU is paid for by medicaire - except since mom has mersa, there is $20/ night for private room. He would have to pay for that.. or can he refuse if I leave him out of discussion of where mom should go? mother doesn't want to cause rift by changing POA. she doesnt' believe bro is a problem

I agree with Jeanne. You are complicating the situation by involving him on decisions that are yours to make. I understand you might want to speak to someone that can help you think through things for her care. It's not him. $20 is not much to pay to get help with MRSA. What would your mom like to do?