I don’t mean to be critical or making trouble but what you’re using isn’t accurate. IMO its important to be accurate especially when discussing firearms and self defense.
.223 Remington isn’t Nato, 5.56 is NATA standard round with the main difference being the chamber pressure the rifles can handle. 5.56 NATO ammunition (60k CUP) shouldn’t be used in a rifle chambered for .223 (50k CUP).
Regardless the energy numbers are highly dependent on the ammunition.
The .223 round will have in the neighborhood of 2800 to 3200 fps and 1300 ftlbs at the muuzzle. The 5.56 NATO round will have slightly more, again depending on the specific ammunition being tested. A 12 ga 2 3/4” shell with 00 will have around 1500 ft lbs at 10 yds.
So there isn’t a huge difference in energy between the two calibers at distances encountered in the home. The only real difference is the 12ga fires 8-12 .32 caliber pellets at a time depending on the shell size. Also, since the 5.56/.223 firearm is rifled it has a longer effective range.
LOL !!!