I have 2x Fire HD8 tablets on the wall for about two years now.
It does for me. I am using custom cards for better control over the layout, but no fancy animated cards.
Yes. I download the package directly from the Fully Kiosk website. There is a special version for Fire OS.
It can be configured to never sleep. I dim the brightness and use the built in camera as motion detector to increase brightness.
I asked Amazon support nicely and they removed ads free of charge.