Please tell us what we'd see in the Zapruder film, according to your theory, if the Stemmons Freeway sign hadn't been there on 22 November 1963.
JFK's reacting to having been hit "at Z-193," or his getting ready to react to having been hit "at Z-193"?
(LOL)
I don’t have a theory. But I can tell you what facts are established by the clear preponderance of evidence:
1. there were three shots
2. the first shot was just after z186 and before z202.
3. the first shot struck JFK
4. the second shot was perceptibly after the mid point between the first and last.
5. the third and last shot struck JFK in the head
6. the above five points means that the second shot was perceptibly after z254.
I can’t tell you for sure what JFK is doing when we can’t see him other than to relate what witnesses observed him do or appear after the first shot. But that varies according to the vantage point of the observer. The only person in the same vantage point of Zapruder was Zapruder’s camera and it doesn’t show what he is doing. But I would suggest that it is reasonable to infer that between z193 and z225 JFK brought his right hand down, moved left and assumed the startled look we see in z225.