I'm answering to myself (once again
)
About #7 : I always thought, and have read several times, that subscriptions can't be shared between Kindles registered to the same account. I don't know if it was always like that, and it's could be certainly be made more easy to do, but on my Manage Your Kindle -> Newspapers page, I can send the latest edition of my subscriptions to my Kindle Non Touch when the subscription was set on my Kindle Keyboard (not to Kindle 4 PC).
I even discovered by reading comments on amazon.com that some newspapers (a French newspaper "Le Monde" for example) have a specific version for Kindle for Android ! It has more pictures, some in color, unfortunately I don't know if the content is different (I guess not). So I purchased today's version for Android, went to my Manage Your Kindle page, I had the option to send it to my "regular" Kindles, but once I clicked "Send", it said it couldn't be delivered to the device. However I can transfer it to my computer and should have a bit nicer version on my Kindle.