Regarding the Kindle $50/$75 promo:
I don't see it
but here's some possible help.
Try
www.amazon.com/gp/feature.html?docId=1002406861 . I see "We're sorry, you are not eligible for this offer." The only Kindle related offer I see is the "Get Kindle now—pay 20% at checkout, and pay the balance in four monthly installments." deal here.
http://www.amazon.com/gp/product/B007HCCNJU/
Slickdeals (where I got the offer URL) has a lot of
drama about this offer if you *really* want to wade through it all. AFAICT, the offer seems to be targeted to specific customers according to some mysterious criteria.