keeping whole litters

Keeping the whole litter does ensure that you will pick the best out of the litter but I would sure be hoping for better than one dog making it. I would be hoping for about 75% of the litter making good to great dogs or I would not be making that cross.jmo.
I normally do what you have done in the past keep 2 or 3 out of the litter & place the rest of them in the hands of hunters.
On the fighting issue & this would not work for you because you said they were about 15 miles or so out in the country. My pups run loose until they or 5 or 6 months old, but they all eat out of the same pan. I stand over them & if one growls, he or she gets corrected immediately. They grow up knowing that growling & fighting is not tolerated & if I do end up with one that just does not get it, then they are culled.