That's awesome, congrats! I am also impressed because I shot a little 410/45 with the 16" rifled barrel and that 410 seemed almost hopeless at killing anything! The patterns were horrible and wouldn't break a clay pigeon on the ground at more than about 10 feet, so I am happy that yours is better!
Interesting graph, thanks for sharing. I would say this is outside spread. I have never had the game and fish measure inside spread on a buck and I think that is usually what they refer to.