I need to get my mother out of the nursing home and into a hospital against the POA of health (my brother) who is neglecting her!

You have, if you reported as you said you have, to the authorities, done all you can.

You say you cannot afford an attorney to make application to be her guardian.
Your claim that the Rehab center is in collusion with your brother makes your story here somewhat questionable.
You do not say what the outcome was of Adult Protective Services claim of financial fraud and neglect?

It is time to step away now, before you are visited with a stay-away order by the courts and have your visitation rights removed by restraining order. You are considering illegal actions now that can result in your being prosecuted and jailed. It is time to understand that you cannot control everything. It is time to understand that your choices now are down to:
1. Assisting brother in the care of your mother and providing supportive and loving visits without rancor and dissention
2. Stepping away and staying out of the situation entirely.

Usually there is a social worker that you can talk to at the facility. They may be able to refer you to someone. If it is as bad as you say at home you may want to contact adult protective service in your area. What
state are you in? If you go to your local senior sites for your city there will be a list of services. There is also an office for the aging. Visit the Elder Care Locator website and Call 1-800-677-1116. 

Don't remove her yourself like that. If you break the rules/law and do this you will permanently end yourself as being an advocate and solution. If you think your Mom doesn't have dementia, then go there with new PoA paperwork, 2 witnesses and a notary and have her revoke your brother and assign you for both medical and financial. You won't be able to remove her without her doing this first. FYI you need a certified elder law attorney, not family law. Then, if you are able to get this far, take her to a primary doctor and have her tested for dementia so that she has a diagnosis/evaluation in her medical records. But you say she needs a hospital... if she's that ill you need to think past your emotions before you convince her to leave the NH. You say you have evicence that your brother was financially exploiting her, yet he hasn't blocked your access to her. Maybe you are misinterpreting what you thought was "evidence"? What evidence did you see? You would need to take this to a certfied elder law attorney to see if you have a case. But, you can't afford to lose, and maybe can't afford to win, either. If your Mom is willing and able to assign you as her new PoA, then you must be realistic about what this means for both your lives as her Parkinsons progresses. Many people with Parkinsons do end up in facilities because of all the physical care they need that their families cannot provide. They also often develop Lewy Body dementia. Your post says you want to get her "into a hospital"... You would start by taking by calling 911 if she has something that is an actual emergency. If not, then you take her to the ER, where she'll most likely be discharged depending on what her issues are. Eventually she will need to go to your home. Is it even possible/practical to do this? Is your home set up for this? What if you find out she has a lot less money than you thought (since NHs aren't free and you don't mention if she's on Medicaid)? You need money for both of you to live on. In the end if this power struggle is over her money/inheritance then your brother (if he has the financial means) may take it to court. Judges don't like when family fights over elders and may assign a 3rd party legal guardian that is neither of you. But he hasn't blocked your visits, even though you've accused him of a serious crime that may be a felony if true. And, we are only getting your side of the story. Go into this with your eyes wide open. May you receive wisdom as you think about your next actions.