Ear and eyewitnesses will lead you astray because they are wrong as often as they are right.
It all depends on how well equipped witnesses are to observe a fact. Counting the shots was not a problem. 132 out of 178 witnesses recalled three shots. The next largest group was 17 people who recalled only two shots. Determining that the third shot was the last shot was not a problem. Determining what colour Jackie was wearing or where she was sitting was not a problem. Determining where the shots were coming from was a huge problem because of the many reflective surfaces in Dealey Plaza. Brandt remarked that there was "tremendous reverberation". That is not a problem with witnesses being accurate in recalling an observation. It is a problem that witnesses were unable to make the observation ie. discerning the direction of the source of shots.
JBC is the key to determining when the first shot was fired.
So why do you not accept his evidence that the car had gone about 150-200 feet along Elm St. when the first shot struck?
He said he turned to look over his right shoulder in reaction to the first shot. So is he right or wrong. We see him start to make that turn at Z164.
The "We" does not include me. He said turned around to look at JFK. He makes not even the slightest attempt to do that until after z230.
So the question then becomes is he turning in reaction to the first shot which happened earlier or is he turning in anticipation of a shot that would come later. That question answers itself.
If you follow the evidence, that was not the turn he was referring to. It was a turn at about the same time as JFK turned to his right and started smiling and waving at Mary Woodward and her group who had just shouted to him. They said that his smiling and waving was BEFORE the first 'horrible ear-shattering noise'.