Absolutely doing the right thing – set clear boundaries and stick to them and maybe tell your mother who is vulnerable to exploitation.
Get yourself some support either from http://www.teenchallenge.org.uk
or google The Recover Course who do 12 week courses for addicts and family support alongside.
Cocaine and benzodiazepines are highly addictive and only rehab will save him I’m sorry to say, so in the meantime save yourselves and do all that you can to stop enabling him.
Call the police or crimestoppers anonymously to report the dealer or even your brother – make him homeless if he won’t seek help. Until he wants to change you and your dear Mum will be used and manipulated.
Heartbreaking but stay strong. Loving him will not be shown by giving him money.
Sending all good wishes for strength and wisdom. xx