Is there anything I (F25) can do to help my mum (F50) and brother (M16)?

TL;DR my little brother is showing traits of his narcissistic father towards my mum. What can I do to help?

For back ground, my sister (14) and brother have a different dad to me. My mum and him were together since I was 3 and she broke it off finally due to him being an abusive narcissistic arsehole that was terrible for the family about 10 years ago. Ever since I can remember my brother has seemed troubled, he was diagnosed with adhd when he was about 9 and would have terrible meltdowns.

Over the past few years this has escalated to him mirroring his dads behaviour towards my mum, being verbally abusive, smashing up the house, being manipulative and generally rebellious/disrespectful whenever he can.

My mum is very poorly and the dad is absolutely no help. He will see my siblings a couple of times a week but we have asked for his help having my brother with him longer term as my mum is struggling and he just won’t as it’s ‘not convenient’ for him. Having any discussions with him ends with me and my mum being verbally abused by him which is extremely triggering for both of us after living with his ways. My mum has spoken to the police multiple times and they can’t do anything. We have reached out to family solutions (preventative step before social services (who have been involved before due to the father) and they set up a plan for therapy for my brother and mum and support groups etc but this was over 6 months ago and nothings happened. I can’t have my brother live with me as I don’t have the space for him full time, although he will sometimes come to stay.

I just don’t know what to do from here, how to help and support my mum and brother and sister who are all struggling living in this situation. What can I do?