Put yourself in his position. Would you act rationally in that situation and think to smash the glass or do any number of other things that would have kept his cover intact?
Sorry, I can't. Momma didn't raise no dummy. If by now he didn't realize the rules have changed, then he is a fucking moron.
Cover? There is no cover. He IS dead.
I think the way it was done was perfectly fine. It adds more drama and Julie was always going to be a love interest for the MC, so it was as good a time as any to introduce her to the world of vampires.
He already met quite a few individuals that kill humans as an afterthought. He is not safe himself, by any means other than being a MC. He does not get to introduce anyone to anything.
Oh, and please don't use "love interest" in this context. Call me old-fashioned but fucking up someone's life in no love. "Fuck interest" is more appropriate.
We will most likely end up with the same teen-drama we know from Rebirth:
- he tells her about vampires
- vampires learn fairly quickly that he told her
- she will end up a ghoul or something similar with the same bloody "boo hoo, why did you tell me, I was happier not knowing" (true BTW)