Can't comment to the expectations (I'd guess it's 24/7 across Amazon), however in a reasonably size team you should not be on call more than a few days every month and Sev2+ event (the ones you have to wake up for) are somewhat rare so it's not like you find yourself fixing bugs in production at 3AM every month.

Very team dependent and dependent on the scope of your production systems (E.g. is Amazon.com dependent on it or is it some random downstream system). There are countless teams at Amazon that get paged 20+ times a week.