2 - I'm not sure that the Kindle for iPad app has any Profiles and/or allows Parental Control (I think this is what you want). If it does then no doubt someone will be able to give you better/correct information and I offer my apologies for giving wrong information.
3 - You create FAMILY LIBRARY using the Amazon website changing the setting on your account to share your content with a different email address amazon account. You can share your library with anyone by simply registering their device or app to your amazon account. You would set them up as "children" profiles and restrict what they can do and see. As stated earlier, I a, not sure you can do this with an iPad / kindle for iPad app.
Here is a direct link to the FAMILY LIBRARY help page on the Amazon Website help page