All of those pictures look perfectly normal. I see absolutely nothing at all that is cause for concern or indicative of unusual wear, damage, breakage or defective parts.
One of our instructors took it over to our range and shot a five-shot group at 7 yards with it. Thanks to the lack of rifling the bullets were keyholing, but he still managed a 3” group.
I definitely agree that it takes something severely wrong with a gun for it to legitimately be grouping 4" at 21 feet.
That's what I was trying to get across with my initial posts. There would have to be something very loose in the gun that was allowing the barrel to move around freely to an unusually large extent. Or something broken or damaged enough to cause lockup to be very inconsistent.
For example, in one of his posts, pblanc mentioned that:
"In the case of my Beretta 92 FS there is a gap of about 1.4 mm between the top of the barrel and the top strap of the slide." That's about right, and it's important to note that even if the muzzle could move over that entire range freely, that 1.4mm of play at the muzzle alone wouldn't be enough to cause 4" groups at 21 feet. It would take more than that--probably around 2mm of play. In other words, there's not even enough room in the hole in the front of the slide to allow the barrel to move enough to cause 4" groups. So the back of the barrel would have to move around too, or maybe the rear sight is loose and moving around. With the barrel loose at both ends, or if the sight was really moving around, those things could account for the kinds of groups you're seeing.
There are other things that could result in accuracy issues. Perhaps the bore is wrecked/badly leaded/defective and is throwing spitballs instead of spinning the bullets downrange. Or maybe there's a big gouge at the crown of the muzzle that's knocking the bullets off kilter as they leave the muzzle. Those things would mess with the accuracy, but as pointed out, even one of those problems would be hard pressed to mess things up enough to generate 4" groups at only 21 feet.
I'm hoping you figure out what the deal is, because if there's something wrong with the gun that's causing that much of an accuracy issue that close to the muzzle, it's going to be very interesting. Especially at this point with all the checks you've done so far.