Am I wrong for feeling this way?

If you're going to talk to your dad, you definitely should not bring up your sister in any way, especially not to compare your actions and contributions. Based on the way you describe your parents and how they treat your sister, if you do, he'll think you're just being whiny and that'll contribute a lot to your "verbal destruction". It's a sure way to failure.

I'm not one to rock the boat, but if there's no long term negative repercussions for just asking, then I don't see why you shouldn't.

Best of luck to you.

This. Remember that while your sister is part of why you're considering negotiations, your goal is to be able to save more money and bringing your sister down isn't going to contribute to that while doing it might spoil any chances you have of talking things out.

You're not bad for feeling this way, it's just that what you feel about it and what arguments you're bringing up in support of your case are separate matters here.