Why the gravity only affects the 2nd level? Inertia. The 3rd level is only affected by 2nd level where there is no gravity, hence, there is no force acting on them. It's like they were sitting relaxed in a couch.
Why couldn't they blame the Joker? Many have seen that the Joker is not in the scene of the crime at the time.
Ok... the matter at hand
My reaction to TDK as the credits rolled was like the way I reacted to A Clockwork Orange... stunned.
Nolan and Kubrick always have the same effect on me. Their film has a coup de grace. I know right after watching that what I've seen is spectacular and pure creativity. But it needs to sink in first. And it demands multiple viewing as their films has so much essential details in it that will affect the film's overall theme.
So how to react to a Nolan film? This is what I do, I always admit that I'm a dumb viewer. I understood the plot. But I've not yet understand the WHOLE scope and magnitude of what it's really about upon first viewing.
A flan in the face