She is specific on what he drinks, where he keeps the receipts after purchase of alcohol, what gas stations he stops at, and what kind of bag it is placed into (paper bag). She is scared for her life when he drinks and drives with her but is afraid to say anything to him because he will yell at her to the point of making her sob (not the first time).
Is her report to you trustworthy, or could she be trying to play one parent off against another? Is she willing to explain all of this to a guardian ad litem (a person appointed by the court to serve as the eyes and ears of the judge and investigate the facts) or to a judge, even if it will make her father very angry?
If you're convinced she's telling you the truth and she answers the last question, "Yes," contact your attorney immediately. The safety of your child trumps visitation for the most part. Ask your attorney what your daughter should do when confronted with this situation -- there are several things I suggest to my clients when they come to see me about such situations, but it would be inappropriate for me to suggest them here since I have no opportunity to gather enough facts to know what suggestion is best.