Re: BC issues
I'm guessing that your reticle spacing was not in true mils. Assuming a 200 yard zero, your 680 yard dope should be about a full mil more than what you reported, and the 1120 yard drops should be about 4 mil more! That leads me to believe that you need to zoom the scope in a bit in order to get true mils.
A non-zero shooting angle at 1120 yards, etc, if not accounted for, may induce a little bit of error, as well.