When Harry first stumbles onto the Circus and the sense of darkness pervades, I thought of the too-soon-cancelled HBO series Carnival. It had that same sort of magical realism about it with a hint of things not being quite right. So in my mind the Circus existed in an odd Depression era America like the series.
I liked Lydia's explanation of why they all belonged with the Circus - because they didn't fit in any where else. I also liked your explanation of crop circles. (I love when stories take a bit of real life and spin it.)
There's a shared tragedy of Severus losing his (human) voice that had always been so integral, and Harry losing his Parseltongue that had seemed so integral.