I'm so sorry you are related to douches. But your dad is just as bad as her, he's just quieter. He is a grown man and he could have (and should have) protected you from her. He gets something out of it. Most likely that when she's abusing you she's not abusing him. Or even more horrible is that he agrees with her but enjoys being thought of as the "nicer" parent while she does all his dirty work. He could always leave her if he wanted to. He's no victim here.

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I'm willing to bet that your mom is a narcissist, your dad is her enabler, and you are the scapegoat. Does that sound about right? Have you ever visited the "daughters of narcissistic mothers" website?