I'm no expert, but I would have thought that you wouldn't follow the target. Surely LHO would have seen the trajectory that the (slow moving) car was going in and settled his aim in front of JFK, waiting for his head to move through the target rather than moving the target to the head. Then once he'd reloaded it would simply be a case of returning the sight to the same trajectory, but slightly more ahead than before. A rabbit would be darting all over the place after the first shot, but the car didn't speed off until after the head shot. I haven't been hunting, but is it really that nerve wracking to shoot a rabbit? The profile the documentary built up of Oswald through his family, friends and acquaintences portrayed a determined almost psychotic individual, I don't think he'd have too many problems with nerves, not like you or I would.
"A shot clearly struck Kennedy, possibly with fatal consequences. Why make another more difficult headshot?"
I'd say, 'why not?'
"All I am trying to point out with the rest of my post is that there are other issues involved and those chosen for this documentary supported the the theme of the programme....the lone gunman theory. "
But the other issues aren't as convincing as the lone gunman theory, Occam's razor and all that.