For meat, with rabbits of that size, it is common to use cages at least 30 inches by 36 inches with wire floors. Each adult rabbit gets its own cage. A bigger cage (36 by 48, or even bigger) would be nicer for the rabbits, if you can manage it.
For cage size, you need a balance of space inside...
That sounds fairly normal. The adult rabbits may eat enough to get fat, but they do have some sense of when to stop.
I do not know what ratio of pellets to rabbit weight, because when my family had rabbits we just provided pellets free-choice to all of them. Most of the year, the does were...
Quantity of pellets will depend a lot on the size of the rabbit.
Some adult rabbits weigh 2 pounds, some weigh 15 pounds, and the different sizes need different amounts of food.
Provide unlimited pellets to a doe when she is pregnant or nursing, and provide unlimited pellets to young bunnies...