I'm so happy that you are going to be able to get out of there.
If you feel your dad can keep the secret then tell him, but if you
even have the smallest doubt that he will tell your mom and your
ability to leave will be jeopardized, then keep it a secret. It is so
important that you get out of there, don't let anything make leaving
even harder. The last thing you need is for your mom to get a hint that
you are leaving.