Bosses who are bastards (excuse my French). A fairly common problem to be encountered in many walks of life I'm afraid, and there's not really much you can do about it. It looks as if you will be losing the job there anyway so you can do anything reasonable within the law you get your revenge, including giving her a firm but controlled dressing down in front of her colleagues, students, and bosses.
Your major credentials for getting work are your degree and TESOL certificate. However, failing decent pre-written references from any previous employers, you could try to get some written citations from satisfied students or their parents.
Your new employer might pass on taking up references, but if you think they will contact your old school, and/or if they ask you directly at the interview why you are looking for a new job, simply tell them, just like you did here. If they don't believe you, and don't hire you, then you have probably saved yourself from yet another nightmare experience.