Furniture can help attenuate the volume, it won't stop the bullets any more than the walls.
The military uses 77 OTM for CQB - meaning inside buildings, or shipboarding duties. Black Hills sells it. You don't have to practice with it, but a mag or two of that ready to go would be a good choice.
As for the experts saying what is or isn't a good choice for deer, the collective wisdom of the conservation departments nationwide is to allow it's use. MO allows any centerfire cartridge for taking whitetail deer. Consider that we apply a different purpose to hunting ammo - our ethical goal is to hit it with enough force to keep the game from escaping and quickly put it down with the minimum amount of suffering. As long as you are shooting within the 1,000 foot pound of force range of a firearm, it's more a matter of competent shot placement.
That doesn't mean that pistol caliber hunters, bow and crossbow, or even atlatl users are being unethical. The competent hunter choses to propel his weapon at the target when he knows it will effectively and humanely take down the game. And the skilled hunter knows how to get in close enough to do the job - considering the habits and habitat, he often has no choice but to do that.
In my case, I'm using a 10.5" AR pistol to hunt dense brushy valleys as that is where whitetail lay up after leaf fall. There behavior in the rut in late fall and where they congregate isn't the same as year round. Keeping my shots under 80m won't be hard, the cover limits visibility to that or less. 5.56 certainly DOES have more than 1,000 foot pounds out to 80m in from a 10" barrel in this case and can do that job well - without having to lug an 8 pound WWI era battle rifle caliber from the days of yore.
You have to know your ballistics application - not just take slanted comments from self appointed experts, which every forum has in abundance. Just ask, they will be more than happy to tell you the other guy isn't right.
As for the use of 5.56 in a combat weapon - the application works there, too, but for entirely different reasons. We aren't trying to get one stop shots on humans at 500m with 5.56. We are trying to get HITS - to reduce the effectiveness of another human being able to return fire in an effective manner. If that human can no longer respond due to his incapacity, the round has done it's job - even with less than 400 foot pounds of force. Again - shot placement is key, not necessarily immediate exsanguination or nervous system overload. He just needs to think he's out of the fight, and that doesn't take nearly as much power delivered down range. It accomplishes the purpose just as well as body bagging him instantly.
It's the typical male ego pattern that tends to insist on that - the use of power for it's own end, not necessarily in the amounts needed to get the job done. If anything, it's the whole point behind the current fad of .300BO - it carries more power, even tho it has less effective range than 5.56.
Keep in mind if you are expecting to have to use a firearm to defend your home against intruders, that many other things will have to go neglected first to even get to that point. Relying on a firearm as your only recourse and it's use after they get in the door is a very poor plan, best categorized as a last ditch effort. It's common enough to discuss it on firearms forums as the focus is all about the gun, but it's also limited and prone to failure.
There are other things more important to be taken care of first - what gun you use in the extreme and rare case all that fails won't really make a big difference. You will want to have well thought out and rehearsed reactions to the threat more than which bullet you might choose to use.
