My mom had Alzheimer’s and cried at night, praying that she couldn’t go to heaven because she was divorced.

"He still lived with her and took care of her for as long as he could."
Who is he? And did he divorce Mom?

"I am being threatened by my brother and his wife that I’m going to jail."
If Mom has been gone for 3 1/2 years why does your brother say your going to jail? What did you do wrong?

I am trying to make sense out of your very confusing post.
Was it you that insisted that your mom divorce her husband when she got sick for whatever reason and your brother and his wife weren't happy about that?
I'm not sure what the legal ramifications there are(if any)pertaining to all that, but I guess if the state attorney is involved there must be some.

You are missing the meat of this post.

What is it specifically that your brother and his wife are threatening you with? What do they claim that YOU have done?

There doesn't seem to be much clarity for whether a person with dementia can choose to get married. It's basically that yes, they can, even with an active PoA -- but this may vary by state. What is the legal issue that is causing your brother to be outraged by this? Your Father was willing, your Mom made her own decision, they were married in the past... does it have to do with why they got divorced in the first place? Can't answer whether or not you were "wrong" because we don't know what harm this remarriage did. We only know your brother didn't like it... but why?

Can you explain more?

What?