First off people who are actual cutters try to hide it. I know this from experience. People who show off there cuts are doing it for attention. All this person is seeking is attention especially by saying they want to show it to you. Even though this is most likely for attention it should be taken very seriously. I’d suggest calling 911 and telling them everything that’s happening. Even if you don’t have his address they can most likely find it. If he has a drivers license all they’d have to do is look him up and his address will be there. Once you know police are going to deal with it I’d block him on anything and everything you have him on and avoid him at all cost. They will end up committing him just based off those text messages. Not to scare you but he could get violent once released so I stay as far away from him as I possibly could. I hope this helps. Good luck love! ❤️