Das,
There is zero reason to insist on a 3-inch shell for reliable "one-stop" use at the distances you're talking about inside a house.
Honest, guy, generations of cops have used non-magnum 2 3/4-inch 00 Buck very successfully on the job to do just that.
You're setting yourself up to fight the gun, not the assailant.
You're also restricting your overall utility. First you talk about carrying your shotgun in the woods, then using it inside the home.
A standard 2 3/4-inch 00 buck load will handle both. A reduced recoil load will extend distances for all-round utility. The Flitecontrol stuff will extend distances even farther, for much greater utility.
If you insist on sticking with your 3-inch Mags, you're beating yourself up and cutting your effective distance way down for absolutely zero benefit.
Much overkill indoors, inadequate range outdoors.
You seem to be having a hard time accepting the concept, but 2 3/4-inch loads will do anything you need doing indoors, and the Flitecontrol will handle any personnel, wolf, cougar, or rabid coyote threat in the woods outdoors.
3-inchers were, as mentioned above, originally a hunting development for birds, and extended into the defensive & fur hunting market later on.
Again- no professional defensive school I know teaches or advocates the 3-inch shell, and no PD I've ever encountered issues or advocates it.
It's simply not needed, and it performs worse in the respects also mentioned above.
Firing from under the armpit increases your chances of a miss, and also makes recovery time longer between shots because of lack of control with 3-inch Magnums.
And, I'd drop the idea of concentrating on a one-shot stop. Fire one, immediately cycle & re-target, repeat if necessary. As also pointed out above, it's quite possible to miss even with a shotgun, and followups should always be a part of the expectation & the readiness.
I was trying out some 3-inchers for function in a new Beretta Storm last week. Even in a semi-auto, those things take longer to re-target. Fighting major recoil while cycling a pump & trying to re-target makes for complication I don't need.
Not trying to be confrontational, just pointing out some facts.
I can "handle" 3-inchers, I just see no point in trying, and I don't mind saying it right out in public.
Denis