ndlc, check our your local area to see if there is a local alanon group. Keep posting here because you will have people who can understand you and give you advice from their own experiences. There is another group called Bottled Up that provide materials you can use at home.
None of this is your fault. Your mother and sister are probably in denial, this is typical of co dependent behaviour. You need to know there is nothing you can do to change your father's behaviour. You need alanon materials to help you handle this.