Re: 1.5 mile head shot on a moving target... not good.
Being somewhat educated and knd of old, and also from a family with a long history of farming, I thought I would give my .02 on these large Amish families. First, the Amish beliefs forbid them from using most modern conveniences, including motorized vehicles and equipment (there are exceptions). Second, this means that in order to accomplish the task of farming, many more man hours are needed to perform the same task that a modern day farmer can do with modern day farming equipment. Third to have the man hours needed for the task, you have to have the men. To get the men at an affordable rate, the Amish farmer uses family members and neighbors. Fourth, it is more cost effective for the Amish farmer to have a large family (workforce) than to use help from neighbors.
If you go back about 3 or 4 decades and look at the size of farm families, you will see that most of them are rather large. Families with 10 kids or more were more the norm than the exception. As kids grow up and move on the farmer has to replace that worker. His solution was to keep new workers in training and in his workforce,by having more kids for workers. Both my mother and father came from farm families, and both were large, with 8 or more kids in the family.
As far as sustainability of such large families go, they are more sustainable than some family of 4 that lives in a big city, because that large farm family grows their own food for themselves and that family in the city.
Oh, one more point. If you look at the modern farmer, his family size on average is the same as the family of 4 in the big city. To cover his workforce needs, he has to hire outside labor when he needs it. Ever wonder why there are so many aliens in the country now, and not 40 years ago?