I agree with the comments who say you should file a complaint with the school. Even if they don’t take it seriously at first, it sets a precedent and builds up a case. If he persists on harassing you, file a complaint against him again. It makes your case stronger. Besides, eventually this head case is going to harass some other woman, who could file a complaint. And the fact that you’ve already filed a complaint will make it easier for her to get something done about this dude. And even if nothing gets done about it, at least you filed a complaint. Because if you don’t file a complaint, and later down the line he assaults you or even rapes you, the authorities will have a harder time prosecuting him if you’ve never filed a complaint against him. So file that complaint. Go along with the fact that he’s a "woman", because you don’t want to shoot yourself in the foot. And whatever you do, do not exaggerate.

Does your family know that you’re a lesbian? And if they do know, did you tell them about your predicament with that creepy fella? If they know and they support you, it makes it easier to deal with this creep. Consider taking up martial arts, like karate or judo.

On a final note, you’re not stupid. It’s not your fault that society has become so unhinged and degenerate to a point where it entertains the delusions of some mentally ill man who thinks he’s a woman. Yes, be careful who you come out to, but you and your friends probably would have been more careful had you and your friends known that trans identified individuals can do whatever they want. And there is nothing wrong with being a lesbian.