You need options? I've got 'em! To the best of my knowledge (take that with a grain of salt, but still), in every state in America, you are automatically emancipated once you become a parent. I had a step-cousin who gave birth at age 13 and not long after, she chose to leave home. Her parents couldn't stop her because she was a mother and therefore legally an adult.
Being on probation, however, I wouldn't just take off and stick your tongue out at the old man proclaiming "nah, nah, I'm a mom so you can't touch me, dickhead!" Before taking any action, you should consult with your school counselor and ask him or her to put you in touch with someone from Family Services who can advise you on exactly what your rights are as a teen parent in your state. Teenage parents typically have more rights than non-spawning teenagers. This is one of the areas were all that "parental rights" legislation actually helps teenagers. Basically, in any area where your child's well-being is concerned, YOU have absolute authority and the power to make decisions. At least, that's how it works in most places. Again, make sure to talk with your counselor and find out precisely how it works in your state.
I'd also like to comment on your mom staying with your dad even though she hates his stupid ass (and apparently with good reason). She took vows to stand by him "for better or worse" and, even though she's miserable, good for her for standing by the vows she made. Be that as it may, YOU have made no such vows. Your mother's decision to stick by her husband has no bearing on your life or the decisions you make. He's in poor health? Well, that's just too fucking bad, from your perspective. It's not your job to care for him and do right by him. It is HIS job, as your father, to sacrifice for YOUR happiness and well-being. He is obviously not doing that and is instead being a selfish prick.
At the end of the day, you are about to become a mother and with that comes a whole lot of responsibiliies. Y'know all of that loyalty and sacrifice that your parents have probably demanded of you over the years? Well, as a parent, you now owe that loyalty and sacrifice to your child, not your parents any longer. Whatever you do and whatever decisions you make, they must be in the best interest of the helpless little life you're bringing into the world. Your parents' best interests (and even your own) are of no consequence. You MUST do what is right for that kid and if getting the fuck out of that horrid environment really is what's best for your baby, then that is what you have to do.
Talk to a counselor, talk to a social worker, and then do what needs to be done. From the sound of things, you need to do it quickly. Good luck.
With Seething Anger,