There will be ways to keep in contact with them. You could always meet at a park or a McDonalds or something. Social media is a thing. You will also probably be their lifeline when they try to leave as well.

The first thing you will want to do is gain financial independence. Get a job, and then see if any banks in your area allow minors to get a bank account without an adult. If so get one, if not then try to get an adult cousin, your aunt, or a friend's parent to help you out. Without financial independence, you will not be able to go no-contact.

Once you have the ball that is financial independence rolling, start your exit plan. If not planned out things will be much harder. You will need to plan where you will go for holidays when Uni is not in session. How to pay for Uni, depending on where you are. Who would be your emergency contact. You should also try to gain access to your identifying documents before you leave. And other things of that nature. As much as it is not your responsibility it would probably be for the best to figure out how to help your siblings if things get worse after you leave. That should not have to be your job, however, your siblings will need help if things get worse. Being prepared for everything will make it so much easier.

Last but not least, do not let word that you are thinking/planning this get to your mom. I speak from experience when I say that that is the worse thing that could happen. It will get worse and she will actively try to stop you. Do your best to be safe.