Hi Need to talk,
Wow, what a rollercoaster you are on, and well done for reaching out for support.
I agree with everything BT has said, look after yourself and be there for your mum. Does your mum know about his cocaine use?
Is his GF a coke user too? I’m assuming so. The problem you have is that 2 addicts are worse than 1, at least if one isnt then that 1 will try to help the addict.
I think it sounds like you wont get anywhere and you’ll just get frustrated because being of sound mind, you’ll want to scream at him.
Take care of yourself, I hope you have friends and maybe a partner you can also lean on for support.
x