Sweetblood, the problem you are having here is not one that is easily solved. Unfortunately, you live under your parent's roof. You are their child. They are the parents and are going to do what they want to do. It is a shame that they will not listen to you. Hitting a pet is not helpful and is, in the end, very hurtful and destructive to a dog's self-esteem. You know this. But, your father doesn't. Unless he posts here looking for advice himself, anything I suggest to you won't make one bit of difference to him because he is not listening to you.
I do not recommend a shock collar. That is negative reinforcement and it is painful to do this to a dog. I hate those things. There are more positive methods, believe me.
As I am writing this, I am actually thinking one thing that might help you. Since we are coming up on Mother's Day, maybe you can purchase a training guide that your Mother will attempt to use and push your father into trying. Since she seems to be the one who is actively trying training methods (such as Cesar Milan), she is the one you need to focus on. She will try to teach your father the techniques that she learns. If you allow her to think that it is her idea to get your father to work on this, that may be the best way to go on this. labman recommends a website for people to look at.
Raising Your Dog with the Monks of New Skete
This is the Monks of New Skete's website. There is a link to their store to purchase their training guides. These men do a phenomenal job of positively training dogs. Can you afford to purchase their DVD on dog training for your Mom for Mother's Day? If you can't, maybe you can buy their book for her. I believe you can order their books through your local bookstore and you should have it in time for the holiday.