Am I being unreasonable?

I feel a little bad saying this but you're mother doesn't sound like a good parent. She is the one being unreasonable. You should not be paying for anything in regards to your younger siblings unless you volunteer to. If you are the one paying for your living expenses when you go to university then she needs to leave you alone. No matter what kind of stress she is going through it is never okay to tell your children that they are killing you or that they want to hurt you. Just go to university, leave the house. You need to be a safe distance from her. She's not a healthy person to be around.