Can you go TOTALLY non contact with your brother?
Perhaps, first tell him that you are not contacting him again and are going no contact.
He will rant and rave about MY son and how he will get a lawyer and yada yada yada. However, as an addict you need to pay attention to what he does, not what he says. Has he ever done what he has said he is going to do? What makes you think he will start now?
Get your evidence and all your ducks in a row. Your first priority is to look after your nephew who calls you Mama.
You and your Mom need to stop worrying about your brother losing his house. Your brother doesn't seem to care if he loses his house - he is too busy being "Mr Party All The Time" why should you care so much?