How do I get help attesting a POA that was signed after my mom had dementia?

The only way is to get an attorney & document everything

hollyambrose: Retain an attorney posthaste.

You need to see an attorney yesterday.

I think you mean contest it or challenge it and the only way to do that is through the courts. My advice is the first thing you should do is talk to an attorney who specializes in this area and tell them the truth, good bad and ugly for advice on whether or not you should pursue anything legally.

This would have to be taken care of through the courts. You would have to have documentation of wrong doing. You will need to seek an elder-legal attorney.

We cannot help in this as I am certain you must realize.
This is a matter for your own attorneys and for your APS (Adult Protective Services) if you have proof of wrongdoing.
Under most circumstances a spouse acts for his or her spouse when they are unable to act for themselves.

If you have proof of wrongdoing do consider and Attorney or APS.

You will need to pursue guardianship through the courts in order to gain legal authority to manage and make decisions for your Mom if she indeed did reassign her PoA to her husband. You will need to talk to an elder law attorney for IL to get professional advice as to what your chances are of succeeding. It can be very costly to do this, especially if her current PoA fights you. If it goes to court, and you lose, you may be responsible to also pay the PoA's attorney's fees.

Please get help from an attorney and not from an anonymous, global forum where you have no idea if we're giving you accurate advice, there are no consequences if we do, we don't get all the details, and may not even live in IL. And, we're not attorneys.

If you want free legal help you will need to research that online for pro bono attorneys in IL. I'm sorry for this distressing situation. I hope you and your family can resolve it peacefully.