This sounds an unlivable situation.
i really hear your anger, the fact that you are holding everything together and helping keep a roof over everyone’s heads and you’ve got your brother behaving awfully and your mum enabling because she’s too scared to put her foot down and rock the boat.
in a sense by you staying there you are enabling them all, if you left your mum would soon see she cannot carry on in this situation and she would hit her rock bottom which I know you are scared of because of worrying she will have a breakdown and not cope financially. This could be the turning point for her.
Also must be so tough for you to leave as you want to protect your disabled brother.
I think the next time he kicks off. Call the police and also call social services re the abuse towards your disabled brother. Maybe call social services first so they have a log of your concerns. Also call police for advice.
What has stopped you all calling police on him so far?
maybe also pack your bags and leave even for a week.
let us know how you get on
xxx