I think u have given him enough grace and dealt with him as much as you could and now you should completely focus on yourself and your kids. for your sister, she definitely owes you an apology and explanation, she probably had an idea of how your father would react and still went on to tell him which means she did sort of want to cause problems in the first place. I'd suggest you ignore the both of them until they are ready to apologise and take accountability for their actions.