My father has terrible gambling problems that are destroying our family, what should I do?

See below . If you are under 18 yrs old talk to a trusted authority figure, your doctor or school counselor. This may sound hard to do but it may allow you and your dad to get the help you need. Sounds like he has no control and needs intervention. Very unlikely you can stop it by just talking to him. He is very ill right now and needs help.
Wish I knew. If you are asking you how can make your father change, the answer is that you can't, but you really already know that. Unfortunately, gamblers anonymous does not have anything like alanon for family members, but i would suggest going to alanon meetings, since the issues are really the same. Get counseling for the rest of your family if your father won't go, helping teach you ways to deal with him.