Just to let you know that i am reading wishing and hoping. I dont have much on advice. Except that, if their system is that toxic, then that is their worldview, and they will paint you with that brush.

Of course it is a good idea to change the things they can, like your nephew not being privy to your brother's teletherapy sessions. As long as somebody doesnt end up paying for it? Im saying that from my experience with my family. If i made a suggestion, they would find a way to twist it.

My mother once said to me, "why are you so concerned about your nephew? It's not your kid." I was dumbfounded. I guess for some people, the village can go suck eggs.

My heart is with you.