I think Doug Horne's summary is the closest to the truth regarding the history of the autopsy "conclusions"...
Nah. Not even close.
Of your four points above (quoting Doug Horne), concerning the supposed FOUR changing autopsy conclusions, two are false.
1. 2 Hits from Behind before 11am on 11/22 as reported by Sibert & O'Neill. This is legit, and stems from the original autopsy conclusions prior to the revision from Humes talking to Perry and finding out about the throat wound. I previously pointed out there's an excellent exposition of the facts of the two different sets of autopsy conclusions (not four) in Lifton's book,
BEST EVIDENCE.
2. 3 Hits from Behind by 11:45pm on 11/22/63. This is false, as it doesn't rely on any first day evidence whatsoever, but relies on recollections made in 1978 by Lipsey and in 1998 by Robinson. There is absolutely no evidence for a three hits from behind conclusion by 11:45 pm on 11/22/63.
3. 2 Hits from Behind (throat wound caused by a fragment of head shot) on 11/24. This is another falsehood by Horne, as it was a speculation of the Dallas doctors (specifically Dr. Perry) on 11/22/63, and the illustration accompanying this reference was even cited by you from a Boston Globe article of 11/23/63. It was Doctor Perry who made that speculation; it doesn't stem from the autopsy whatsoever, and it doesn't stem from 11/24/63 as Horne claims. The story accompanying the picture you cited even says
"more complete details are not expected until the autopsy is performed..."; clearly, the story was written on 11/22/63 and published the next day.
The story also says:
"The rather meager medical details attributed to Dr. Malcolm Perry, the attending surgeon, described the bullet as entering just below the Adam's Apple and leaving by the back of the head. Since that statement Friday afternoon, it is believed from determining the site of the firing that the bullet entered the back of the head first and came out just under the Adam's Apple." Clearly, this is a speculation of someone at the newspaper based on the speculation of Dr. Perry. But the key point is this is just monkey business by Doug Horne in attributing this to the autopsy.
The speculation about a connection between the head and anterior neck wounds came originally from Dr. Perry, and it's important to note those are the only two wounds the Parkland doctors were aware of on 11/22/63 - the large wound in the head, and the small wound in the throat. So Perry speculated one bullet could do all the damage, by entering the throat, hitting the spine, and deflecting up and out the large head wound. He was wrong about that.
Someone at the newspaper (unattributed, but most likely the author, Ian Menzies), understanding the shots came from above and behind, speculated Perry got the direction of the bullet travel backwards, and suggested the bullet entered the head and exited the throat. He's wrong too.
Here's the link to the complete story as published:
http://www.the-puzzle-palace.com/Globe11-23-63.jpg
Here's your post with the image from that article:
http://www.internationalskeptics.com/forums/showpost.php?p=11585798&postcount=2156
Your post even references a speculation by another Parkland doctor (McClelland) in his 11/22/63 memorandum for the record that the throat wound was caused by a fragment. Given that, I fail to understand why you can't see through Horne's argument about this speculation stemming from the Bethesda autopsists' conclusions on 11/24/63, when it's clear it stemmed from the Parkland doctors' speculations on 11/22/63.
4. 2 Hits from Behind, throat wound caused by transit of bullet from back wound. This is the revised conclusion the autopsist reached after Humes spoke with Perry and learned of the throat bullet wound. This is the only revision the autopsists made, and it is admitted in the autopsy testimony of Dr. Humes.