You can ask your mom to move you to different school if you feel uncomfortable at your school.
Don't worry about your mom being alone.
I have been happily living alone racing my daughter.
It's better to be alone than have garbage scumbag people in your life. I am sure your mom will feel the same.
I am glad Dave is out of your life.
Be brave and testify against him. Don't be afraid.
Keep remind yourself that you can do this -solve your problem.
Good luck.