Personally, if I were you, I would stop giving your mom every cent. If you decide to continue to live with your mom, sit down with her and discuss a reasonable rent (your entire paycheck isn't reasonable).
And then I would sit both of your parents down and tell them that they had no business involving a child in their fight. And that you refuse to mediate, you refuse to let them continue to put you in the middle. You and your siblings should have been protected from their divorce and their disagreement.
If they want to waste their money on court battles instead of helping their children through college, that is their choice. Tell them to leave you and your siblings out of it.