True.
I estimate about 1300-1400 feet.
True.
Only, he (the LT) didn't initiate the backup. The dispatcher did and the Lt was even hesitant for dispatch to send them.
If your theory was correct and according to the time line of the radio traffic, the LT was in his car, when the trio came into site walking towards him. And, according to the aerial maps, they would have been about 1300 to 1400 feet apart (min.) That's quite a distance for them to be apart on foot.
When I listen to what the LT said on the radio, there was three minutes between the time that the LT said he was going to be out of his vehicle and his next transmission that said they were going into the woods.
No sound of the LT running towards them to close that distance. Just a casual subdued tone with no urgency to send backup.
Aligning all this with your theory. . . What do you propose the suspects and the LT were actually doing for those three minutes?