I answered the first question but neglected to answer the second.
Yes i have discharged a firearm inside a structure.....
I spent 15 years as both a volunteer firefighter and a paid EMT back in the late '70's and 80's in a fairly rural suburb. About every other year somone in our coverage area would allow us to burn a house, barn, shed etc. partially cause they wanted it torn down and partially because they knew we liked the practice, the papers would come out and cover the drills, the owner would get an atta-boy and everyone was happy.... ok we were firemen we really like burning things as well. Often we had days or weeks where we knew we were going to burn the house, we would sometimes go out and salvage stuff (I got a hand carved 1800's mantel from one for my house). Anyway one time we had an argument over home defense and the virtues of shotgun vs pistol, penetration, safety etc. I remember this like it was yesterday, we asked the chief if we could test some theories. He rolled his eyes and said "hmmm no potential for an embarassing headline here... OK but wear your bunker gear, helmets and visors and if anything comes out of this your on your own..... but let me know how it goes and what you find out."
so we shot up the inside of the house, it was loud but not overwhelming probably because most of the windows were broken out already. old fashioned plaster, lathe and wire is pretty good at stopping just about anything, and no real penetration through two layers with anything. Sheetrock pretty much everything penetrated both layers but my shot gun with #8 the pellets mostly stuck on the far (opposite) side of partition walls and the few pellets that made it though just bounced off the far wall (3rd layer). Thats why my home defense shotgun is loaded 2 rounds #8 then 3 rounds 00 buck. i figure after the first 2 rounds i'm awake clear headed and know exactly what i'm shooting at and whats behind it, or possibly even shooting at taillights.