A good rule of thumb is that 12 lbs of honey into a 5 gallon batch (the rest water) will yield about an 11% ABV dry mead. So for 12%, add an additional cup or two of honey.
At the level that you plan to use those Satsumas, they will only be adding flavor, and very little in the way of additional fermentables. So, add them to this mix, ferment to dryness, and then backsweeten to taste. That would be my suggestion.
The original gravity, if you used 12 lbs, would be around 1.090, with the satsumas added. If you want it to be semi-sweet, add honey until you bring the final gravity back (from where it ought to first finish - around 0.998 ) to around 1.006-1.010.