Hi FJM,
Welcome to the Forum.
Please get someone else involved, your too young to deal with this on your own and your Father needs help. I would talk to your Grandmother or Auntie as soon as you can, you do not want your Brother being in the car with him whilst he is under the influence of alcohol.
I hope this helps and your certainly not a coward. This is a great Forum for support.
Take care.
Dx