I can't answer all your questions, but I'll make a start.
1. Based on requirement 4 (sourcing from Amazon), I'd say the Kindle is best for you. I think requirements 1-3 are pretty similar for Sony and Kindle.
2. Sorry, not a Kindle user. No doubt somebody better informed will let you know shortly.
3. See my previous answer

4. No.
5. Probably not a relevant question in light of the answer to 4.
Hope you find something that is right for you