Yes, it is true that the Lewis and Clark expedition reported consuming on average 8 lbs per person per day of venison and elk. Bear in mind that it wasn't only meat they ate, for they were able to forage Camas, berries, and barter for other items from the locals. They needed that much because of the amount of work they were doing.

Rabbit is a healthy protein source in the diet. If you add a little starch and fat, such as your mother did based on your description of the meals she cooked, then you enjoyed a well rounded, nutritious childhood it sounds like.

The problem is with eating just rabbit and nothing else. You would get the same effect eating whitefish, or squirrel, or any other lean meat and not having anything else to consume.

One thing that Lewis and Clark had, which contains protein, fats, carbs, and lots of nutrition in a small package, was pemmican. Pemmican was the survival food for injuns, explorers, trappers, pioneers. Hudsons Bay had standing orders with many tribes for regular procurement for their trapping troops.