The front sight focus makes sense to me, applies to pistol shooting as well which I am much more familiar with, not a rifle expert by any means, but seems you two know what you're talking about so I defer to your judgement.
Plus, I like your stories. 
The difference in rifle shooting as opposed to pistol shooting, at least according to Marine Corps instruction (and yes I qualified expert in both), is this:
In shooting a rifle such as the M1 Garand or M14 (not so much the 16) you aim at 6 o'clock on the bull/target.
In pistol shooting it's "point of aim, point of impact." In other words, you aim at center mass of the target, not at 6 o'clock on the target, which you probably already do.
The 16 is a whole 'nuther different animal altogether, both in sighting and in targeting. The fact that the would be Butler assassin chose a similar weapon (AR-15?), and got as close as he did was shocking to me, but as I understand it, he was using a scope.
So on iron sights there is still a fixed "zero" distance, right? So depending on distance +/- zero distance you have to adjust up or down...then windage affects your horizontal, right? I need more work with rifles, iron sights and scope. Think I might need to find me a Marine, think I got some options around here, got some vets with experience in SEALs and Army around here too.
If your piece has adjustable rear sights (windage and elevation), the first thing you need to do is get the correct zero (called dope in the Marines) for that piece. The way to do that is set up a target 100 yds away, set windage and elevation at zero, and fire three shots at the target trying to get a tight group. If the group is off target, adjust the windage and elevation to move it on target, assuming they adjust the same as the M1 or M14, i.e., one click of either windage or elevation will move the impact of the bullet 1" for every 100 yds. Whatever setting you arrive at will be the correct zero for that rifle, and should be set every time you start to use the rifle. Adjust according to distance and wind when necessary using the same "formula" (1 click will move impact 1" for every 100 yds).
If your sights adjust differently, learn what they do to affect the impact and still follow through with this method of getting your rifle's zero setting.
The AR-15, if like the 16, is very different. I remember getting the zero on our 16, we shot at at a small head and shoulders target only a short distance away (25' I think it was or maybe 50'). I shot a 3 round group so tight you could cover it with a dime. Off target, so the instructor gave me the the correct settings to put me in the black. Was to shoot 3 more rounds to ensure the correct settings, but the thing jammed. So, the fourth round I ever fired on a 16 jammed the thing. Never had a whole lot of confidence in the 16 since.
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BTW, did you see this:
Declassified JFK File Confirms CIA Rejected ‘Lone Gunman’ Theory Weeks After JFK Assassination
https://www.thegatewaypundit.com/2025/03/declassified-jfk-file-confirms-cia-rejected-lone-gunman/I think the headline is a little misleading. From what little I read of it, it sounds like they had their Florida offices looking into possible Cuban connections.
