Oh sweetie, I'm so sorry your family is suffering hardship... being a single Mother is the pits, and trying to find support hard. Everything feels a million takes more difficult, and nothing seems to ever go right sometimes.
I hate bullies, and this jackass is definitely one. A grown man arguing the toss with a youngster? No excuses, no matter how verbal your brother was, he's still supposed to be an adult! What's the matter with the idiot! Oh of course, I get it. He's probably too thick and uneducated to do anything other than bully people to make up for his inadequacies, peasant....😡.....
If you can, why don't you try contacting his company? If that's not plausible how about letting the police know what happened, and showing them the pictures and details you have?
That sort of cruelty to vulnerable people is thoroughly unacceptable, and he needs to be dealt with in a way that will make him think twice about picking on people.
Not much help I'm afraid, but I do hope someone comes along with better advice soon.
Wishing you and your family better times ahead. 💖