Hi Bella,
Sorry you are going through this....I know how much it sucks. I think you are absolutely doing the right thing by keeping your distance from your family. As stressed out as you are now, you would probably be even more stressed out if you were more involved in their lives. It seems that your parents are trying to "cure/fix" your sisters problems (we know how well that works out) and don't understand why you're not trying to do the same. I really admire the strength it must take to hold your ground and stand up to all of them.
I'm glad to hear that you and your family will be traveling, it will give you a chance to be farther away from the drama. I suspect some members of your family may try to guilt you into staying, but everyone has the right to live their own life. It seems that you are choosing to do so in a healthy way and I hope that one day in the near future, your family chooses the healthy path too.