the average is 7 but some can have just 1, and some much more than 7. I don't know the average that die, if you're a good breeder, and take care of your bunny well, I think none probably will die.
It depends on the size of bunny. Smaller breeds will generally have anywhere from 9-16 kits at a time. Larger breeds can have up to 25. If you are asking how many they can deliver at a time, it is...