I think I can help you guys out on the last question. Dr. Alvarez charted the four "angular accelerations" that he associated with loud, startling noises.
He posited a first shot at 177, a second at about 250 and third, which he suggested might be a siren, at 285 and a fourth at 313.
Of course we see dramatic reactions following 285 and 313, beginning at 290 and 318, associated with each of those "noises".
But we see no such thing following 177 and 250 and in fact, pretty much everyone these days, including Posner and Bugliosi, reject shots in those frames. There is a reason for that.
Neither of the first two shots startled anyone, including Abraham Zapruder. So Alvarez was forced to go with false positives.
Oswald's rifle was proven to generate 130 decibel sound at street level. That's 16 times louder than 90db, which is the level at which involuntary startle reactions will occur, as well as hearing loss with extended exposure.
So, it is not surprising that the people closest to the President were startled by the unsuppressed, high powered rifle shots at the end of the attack.
http://jfkhistory.com/duckstwice.gif
But the absence of such loud shots prior to 285, proves that a much different kind of rifle was used to first those shots than the ones at the end. So, unless Oswald was firing two very different weapons, there is no way he could have fired all of those shots.