You are in a situation that every parent needs to face at some point - when they realize they need to let go of their child who has become an adult.
Your parents will probably find it more difficult than most parents to let go, because they chose to move to a different country and at some point decided that it was too much effort to continue to adapt. Instead, they lean on you to carry the load on their behalf.
I would suggest that you decide for yourself how much contact you want to have with your parents in the future, and then make your plans accordingly.
If you want to make a clean break (in other words move away and only see your parents occasionally and on your terms) I would suggest that you identify some support for your parents in your community, e.g. their friends, the church, a community center that they will feel comfortable with, and speak to some people who can give support to your parents when you are not around.
I would ignore the guilt trip from your sister who would love you to shoulder the full responsibility so that she can lead her life.
Speaking of guilt - no matter how much your parents sacrificed for you, they chose to do so and of course you will be grateful for the rest of your life, but that does not mean you must sacrifice your life in return.
When you move away, you can probably expect your parents to be very angry and even to refuse to speak to you, but that will be their choice. You are no longer a child, and you can make your own choices.
On the other hand, if your parents will drive you mad with phone calls, you may want to get an additional phone and listen to your parents' messages only when you choose to do so. That means you will still have contact with them, but you will also be able to lead your own life.
In my experience this is the kind of decision that benefits all, even though people may not agree. Without you your parents will have to take full responsibility for your life - but at the same time without your parents you will have to take full responsibility for yourself.
Above all else, continue to love your parents, no matter what you do and no matter what they do. That will help them most of all, and it will also help you feel good about yourself and strong while you start to build your own life.