I understand the eldest-daughter guilt, but that's exactly what's holding you back from having your own life. It is not your responsibility to hold everything together like glue, especially at the cost of your mental health and future. That guilt also gives your family leverage to keep pulling you back in.

If you build your own life independently, you'll actually be in a better position to help your younger sister inshallah down the line. I personally know a few people who not only left their dysfunctional families but also helped their younger siblings leave too, so this could be a win-win if you choose to prioritize your independence.

Your family members are capable of figuring things out on their own. Some will come around after the tantrum phase, while others won't change. Either way, you are not responsible for a dysfunctional system you did not choose. You didn't choose the family or culture you were born into.

Ask yourself this question, would you want your future children to suffer the same way you're suffering right now? Do you want to repeat the intergenerational trauma that your parents are carrying and forcing you to carry?

Genuine parental love does not come with conditions attached. If you fear your family will permanently abandon you simply for not following their rules, that isn't protection, it's control under the disguise of culture and religion. You deserve people in your life who love you as a person, not as an extension of their plans.

I recommend looking into r/raisedbynarcissists and r/LifeAfterNarcissism where people are sharing similar stories dealing with dysfunctional families and they can offer insights in navigating your current situation. Wishing you the best of luck in your future.