Hey, I’m sorry this has happened to you. Maybe you should consider speaking with a lawyer? You have rights under the Americans with Disabilities act. You have the right to a non-hostile work environment. The behavior of your manager and coworkers is unacceptable and so is HR’s response that they can’t do anything about pens being thrown at you. Your employer has a responsibility to protect you from any sort of physical violence from people in positions of power over you, from sexual assault and harassment to having things thrown at you. If this were a sexual harassment claim HR wouldn’t brush it off like that. If you are at the point where you come home crying, something is wrong, and it’s not you. You have the right to stand up for yourself. You are not the issue here. Don’t let them tell you that you’re overreacting or that you can’t take a joke. You don’t have to live like that.
Sorry if that sounds pushy. I know that sometimes people blame themselves, or that they don’t want to make waves. I do that sometimes. I just want you to know that you are not the issue. They are. And if they treat you like that, they will treat other people like that, too. You are not at all causing a problem by speaking up, you’re solving it. I hope that helps and I hope it gets better.