Jeffbert is probably your main man on this question. Mostly wanted to mention that Tezuka's robots also have robot laws akin to Asimov (you aren't imagining that), but Tezuka seems more concerned (IMO anyway) with possible allegories between the way people may view robots in the future and the social inequalities of today. Tezuka was a fan of science fiction and given how early some of Asimov's stories are, he may actually have read them.
As far as Astro having a human heart, as I recall that may be more of a 2003 thing, but honestly these elements are changed so often as Tezuka continued to reinvent the character that I don't recall off the top of my head.
I think you might enjoy some of the issues regarding robots that come up in the Phoenix series vol. 5 Resurrection. It also is being treated with much thought in the Pluto manga (which is a re-imagining of Tezuka's Greatest Robot on Earth Astro story.)
Anyway, I don't think I answered most of your questions, but I'm deferring that to Jeffbert, our resident Astroboy expert. Welcome to the forum!