Move out now! Take any future checks to a bank and deposit them, and tell Mom you want your 250 bucks back. Your mother is trying to establish control over your life, I went through the same issues with my mother 12 years ago, the only cure is to get out of their house and be your own man.
Keep your head up Richie, your a brilliant guy you'll come out just fine. The best revenge now is to live well. The organization has trained your mother in the belief that seperation from the Society leads to peril, spiritual and financial. Find a roommate, enroll in college and move into the dorms, join a good church and network with them for new friends.
Your mother has no right to take your cash or possessions.