This might sound like a cop out, but you need to understand that your father will not change himself but will let this develop in his mind like a cancer.
You however have a lot going for yourself. There is a website www.asca.com
and this site has a 21 step program that you can print out and start working on. Your sister also needs to work on her own healing. Try and find a MS meeting around your neighborhood and go for therapy, preferably with a therapist that knows about MS or CSA, they don't all. You also need to talk to someone, this thing is hard and if left untreated it will fester.
Remember that above all THIS WAS NOT YOUR FAULT. you did not ask for it, did not want it, invite it, or provoke it in any way. You were a CHILD a small helpless child looking for love, normal love.
PM me if you want, but mostly ask questions of the wise on this site, there is a world of information here, and it all helps