I'm going though the video, much of it is fog of war type stuff -
The guy in the woods was a hunter or hiker, folks in that area all know that school abuts a wooded area.
The assault rifle pulled from the trunk is a Saiga shotgun. You can see the cop clear a red shot shell from the gun. Also the stock and magazine styles doesn't fit AR style profile.
As far as accuracy, these were across the room distances, not thousand yard shots, it's like pointing your finger with a stable platform like a rifle.
As far as witnesses and fathers, it's all to be taken with a grain of salt. People in shock tend to see things that aren't there, reporters take babbling as fact. The father was trying to put the pieces together in his mind a day after the shooting. People after tragic events laugh all the time, it's a coping mechanism to stop reality from setting in.
Who knows who's running that memorial fund, it's probably not even the family, but a friend or some such. Also taking an internet site as proof of age ?
.
As far as leaving Lanza and the mother for last for autopsy? Who cares I doubt the M E was worried about proving himself to wackos.
He probably took them in the order they were received.