I'm going back on my word to financially support my mum and don't move in with her
I am surprised to hear you would go back on your word. What are you scared of that you don't want to live with your mom?
The moment I live with her, I will get physically ill.
I'm sorry your mom is giving you a really hard time, but she is still your parent and you must support her and keep your promises. She took care of you, so you need to repay and keep her company.
She's going to die soon anyways. What points does she have from me supporting her if she dies?
Whatever happens, you have made a promise and it is wrong to go back on your word. Your mother could be left in a very bad place if you do this.