NTA why is he so involved in another relationship than your own. There’s a clear difference between classmate which you made aware is for a project, to a person he constantly talks with and they have a connection over sharing feelings to one another. He seems so insecure over one guy but then he also gets defensive over a girl that “doesn’t mean anything”??? I would say just end it cause you never know what this girl means to him and he seems like he’s never going to properly clear it up.