[Dawn.]

Hi Lucy,
I'm sorry to hear about your dad. It is never easy to watch a loved one struggle with substance abuse.
My only advice is to speak to your dad about how you feel and that you will be there to support him. As others have said, he will get the help he needs when he himself is ready.
You can always get in contact with groups that will be able to not only support your dad but you and your family as well.
I'm sorry I couldn't be more of assistance, but I hope I did help to an extent.