Good and thorough review as always Jeffbert.
You mention that "Atom, stung by the injustice of humans owning robots, is determined to rescue her". I don't think he's angry with the fact they
are possessions, so much as he is angry with the fact they are treated
like possessions (or as you eloquently put it, they are regarded and abused as chattel).
It's something that's always in the back of my mind with Astro Boy stories; Tezuka is trying to portray robots as close to humans as possible, but the closer they get the more prickly a subject their ownership becomes.
I am woefully behind on reading and watching Astro Boy, so maybe you (or someone else on the forums) will be able to tell me; does Tezuka ever directly confront the topic of robot emancipation?