If they threaten to do damage, communicate (in writing or recorded) that you will press charges if there is any damage done. Remind them that a criminal record could have a life-long impact on them. If you can include law enforcement in any face-to-face conversations, even better. But don’t annoy the police. You may need their help later. I’m going to say NTA. Though I don’t know if *kicking him out* was exactly ‘necessary’, you are well within your rights to rescind any and all help that you provide–which sounds like a lot. He’s a grown-ass man.
He’s young, sure, but he’s an adult who has the ability to 1) think about the choices he’s making and 2) understand that there are things that you absolutely do not joke about. This behavior would be unacceptable in a middle schooler. I personally would have raised their rent (as I assume you’ve lowered it to be kind to your brother) and stopped assisting everywhere else, maybe even gone no-contact other than to collect, but I cannot call you an AH for reacting how you did.
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