To clarify, I don’t think that he’d cheat on me, I just don’t know this girl so I don’t 100% trust her. I also wanted to set a boundary about this specific issue with him.

I'm going to address this point mostly. The "I trust my SO, just not other people!" is a long way of saying "I don't trust my SO." Because unless you think she's going to rape him, if you truly, 100% trusted your SO, other people's intentions wouldn't matter.

As for the nickname here, eh, I give a lot of friends nicknames, so I can sort of see his side as far as having it in the first place. But Queen Honey Bun is rather over the top, especially if you have a girlfriend. It wasn't cool of him to be so dismissive of your feelings, but is he maybe being resistant because he can sense your lack of trust? Have you all had any situations in the past where you told him "I just don't trust other girls" or anything? Is he generally a stubborn person?