Leadchucker,
I don't know how you arrived at your COL, but if it doesn't interfere with magazine loading and feeding, then you'll probably find that seating out until the head of the case is just flush with the back of the barrel where it meets the breech face (usually a barrel extension), that you will get best accuracy. To set this up, you just remove the barrel and use it as a gauge. When you have this condition you are headspacing on the bullet rather than the case mouth. I've had it cut as much as 40% off group diameters fired from sandbags and reduce leading significantly in the .45 Auto.
As to charge weight, if they all shoot the same, then the lightest load will batter and wear the gun least. It will also let the brass last longer and cost the least to use. The warmest load will exhibit the least drop at longer ranges (like plinking at 100 yard water jugs).