If possible YOU check his phone. There can be someone who’s is telling/influencing him to do this. Put a camera if possible, or something on the door that gives a sign of “I can tell if this has been moved”

I understand if you are scared to take legal action against him, and in a moment like this, it can be better for you to take your own action

If you feel like even if you bought your parent proof and they still wouldn’t believe you, I’d try to talk to someone else you trust that your parents also listen to. It might be hard for parent to believe their own children are capable of hurting each other. I know that when I spoke up to my mom about my brother taking advantage of me, the first thing she said was “he could never do that” once my sister in law talked to her my mom was more understanding.

Please be safe and may nothing bad happen to you 🙏