What to do about spousal abuse?

It sounds like your Dad is willing to take the abuse, because he only has her to take care of him. I'm guessing your unable to because you work or something. So anyway, if you can find out what he could do if she were not in the picture, then maybe he would press charges. Like if he could get nursing or be in an isted living facility etc. Maybe you could call Senior Services and ask them what they might provide. Explain the situation that he's taking the abuse, because he doesn't have an alternative. Maybe call his doctor and say the same thing...or even better if you could take him to one of his appointments without the step mom, you and your dad could explain his situation and ask a doctors advice. Then make sure it gets put in his chart. Then tell INS to get your dads medical records.