[gremlin]

I don't mean to sound rude but why have you continued to bother with him when he doesn't seem at all interested in you? Why would you tolerate his reaction to you seeing another man when you two are not even together to begin with and he has absolutely no say in what you do in your personal life? And why do you tolerate him when you two seem to have an unhappy relationship and you aren't even romantically involved? Just asking.

Anyways I would send the letter to his mother especially if he is acting irrational and making threats.