I am so so sorry for what brings you here. The disappointment and fear must be huge. I think you will have to do whatever you can do keep your brother out of that situation because he is clearly in danger. Even if you have to hotline your own father, I myself would do so. It's clear your brother needs an advocate.
My heart just breaks for you. Do you attend Alanon or Celebrate Recovery?? That may help you deal with this and get some face to face support.
Tight Hugs.