Some of the comments here are mind boggling! How can anyone agree with this? I personally would have caused a scene the first time I met them. What is he thinking.
People are saying "you should think of your dad", but I personally believe you should think fuck him and his feelings. He is showing predatory behaviour. you also told us he has a short temper and fuse. His new "girlfriend" will make him angry since her inexperience will annoy him some way or another. I firmly believe this cannot result in a healthy relationship, ever.
People saying gratz on your dad for scoring a younger partner. Please ignore these people they are not healthy in their minds either.