The birchwood target itself looks like a weak .410 pattern, so I can see why you are taken back to know that this is a 3.5 12-gauge pattern. Couple of things, I had great luck shooting longbeards out of a regular 3 inch chamber, but I have heard of plenty of folks getting crazy patterns, with longbeards. Almost like they either love them or totally hate the pattern they throw.
We know that the IC .675 is a winner, and your gun has shot well in the past setups from what you said, so I think it is the shell and that particular payload. But looking at your number six pattern with a 3" shell, I think that is huntable for a short trip to New England. 163 in the ten will kill anything at 40 yards, and if you can site your gun in to hit at the base of his wattles, you seem to have a good bit running high (based on the pattern posted) just outside of your ten circle that would then eat him up in his head and make that load even more formidable.