
Idc what anyone says, break up over text. When you're not hearing or facing them its easier not to get manipulated into staying especially because you can block him right after. If he threatens self harm, might sound crazy but tell him you're calling the police or self harm line (bet you he won't do it again if you follow through).
If he says he’s going to hurt himself, call 911. He will either be saved or feel stupid when first responders show up with noise and flashing lights in front of the neighbors. From personal experience, shame works. I sent an email to officers about a narcissist’s bad behavior X, and the narcissist found it. They threw a tantrum, lied, gaslit, but never did X again.