He drew attention to the wand after Hermione committed herself to going to the cage. Maybe he didn't have to, but that's the sort of cleverness I expect from him. It tricked you, after all.

Why do people keep assuming Quirrell thinks of Harry as an enemy?

I can't speak for people, but Harry is Voldemort's enemy in canon. Until I see some extraordinary evidence to the contrary, I'm going to assume that hasn't changed.