I’m very glad you wrote. My guess is that your mother is in some way dependent on her father for help. She is also in physical and emotional pain. It’s likely she can’t find the energy to consider a move. When you bring it up, it may make her feel terrible that she can’t take care of the two of you on her own. It’s easier for her to be angry than to face how helpless she must feel. Those are just guesses, of course. Only you can determine if they make any sense.
Whatever the case, this is far too big a problem for a 14-year-old, even a 14-year-old as mature as you are, to handle alone. You need to find a school counselor or another sympathetic adult to help you talk with your mother. A counselor or someone else in the helping professions will know if there are public resources available to people who are disabled and in need. It may be that there is subsidized housing available as well as other benefits. Your mom may not know what they are or how to apply.
Please take someone into your confidence. You and your mother have been through so much. You need and deserve some practical help as well as emotional support.
Whenever you need someone to give you some encouragement, consider calling the Boys and Girls Town Hotline at 800-448-3000. Counselors are available 24/7 to help teens who are stressed out. Talking with them is free.
I wish you well.