The first sentence is correct. The second is not. See my compilation of their evidence. Few witnesses quantified the time intervals. Many indicated that the spacing was longer than a second.
I see your first witness is high-confidence. No surprise. Poor Bob Jackson is fast becoming your "star witness".
Please explain how your second witness, Linda Willis, could see the President slump about the time of your first shot.
Rather than during the first two shots, Hurchel Jacks could just as well be saying Youngblood got into the back seat during the last two shots.
"He climbed to the rear of the seat with the Vice President and appeared
to be shielding the Vice President with his own body. At that time I heard
two more shots ring out."
But we know Youngblood didn't hop over the front seat even then because Johnson and him are seated in their respective seats in the Altgens photo.
Lady Bird doesn't specific shot spanning. I don't why you include Paul Landis, presumably because he did so much during "the interval between the first and second shots" that it supports a 1.......2...3 span. But, as you point out, he's a two-shot witness, so he could be doing all that during the last two shots or over the span of all the shots.
And that's just the first two pages. You can't get anything over on this Forum. Do you really expect to peddle this nonsense to a panel of jurists or government panel of experts?
Greer said he turned around AFTER the second shot and he is already turned around by z282. All you can really conclude is that the last two shots were closer together.
Why Z282? We can see enough of Greer's face by Z277 to know he's turned around about as far as he ever got. The film also shows Greer turned around by frame 273 (when we first see his hairline clearly; it's the same as later frames).
Greer is probably turned to his right in the Altgens photo. The Greer "head" dimensions and placement shown above are consistent with my 3D work on it so far. When, in Z294, we get to see clearly Greer's head not turned so far backward (but still turned to the side), only the forehead is sunlit, just like the "face" in the Altgens photo.
Kellerman begins to turn his head to his left about the late-Z240s. Possibly, both Greer and Kellerman heard Connally shouting beginning at Z242, which finally prompted them to look back. In Greer's case, he said he heard the second shot before turning his head.
This doesn't do much for your "second shot" at Z271. You have to learn to follow the evidence.