a gunman, a young man, who grew up shooting guns... and more to the point, grew up shooting this gun...put himself at an elevated position, somewhere between 150 to 200 yards from the target, hit CK in the neck causing a massive amount of bleeding.

We have a video of someone on the roof where the shooter put himself ( likely the shooter ).
We have a horrific video of the instance the bullet hit the neck.
Nice sunny day with light winds.

Easy shot for a skilled shooter. Especially one that had used this same gun most of his life.
We have the gun being left behind in some bushes. Perhaps the shooter left DNA on the gun, perhaps he put some markings on the bullets or the shell casings.
We have the young man being captured on various campus video cameras before the shooting.
We have likely positive ID by his father. And he surrendered after being confronted.

Lets leave aside the motive, the text messages, the religion, the sex life, etc.

At this point I would say "there is very little chance that the police have the wrong guy" and as for other involvement I don't see why there should be any.

Conspiracy theory? There really isn't a need to invent one. there really isn't any doubt any doubt the kid did it. Why he did it might be open to a lot of speculation and conspiracy theories... but I don't think we need the medical examiners report or anything.

...was whether or not he was wearing some type of bullet proof vest, and did the bullet hit the vest and deflect the bullet to the neck.

But my (admittedly limited) understanding of bullet proof vests is that they don't actually fully deflect bullets but rather blunt the impacts to a great degree.

certain types of "bullet proof" vests might cause the bullet to shatter and I suppose it is possible that a fragment, deflected, could have killed CK but severing a major artery or vein in the neck.

Depends on the type of vest and the type of ammunition I would think.

Hardly worth a JFK style investigation into "magic bullets" and second shooters, etc.

CK's neck literally exploded... and he bled out. Even if there was a trauma surgeon just off stage with a staffed OR, I doubt CK would have survived.

Otherwise you wouldn’t be asking about an autopsy report. There was no question about his manner of death.