At what age do males "normally" start to come back together that is the ones who really go ugly? Some males just never go through the uglies! lol

Uff... LOL
I know it's a waiting game as it is with everything regarding breeding and dogs 😇

Length of body ....measured from withers to point of rump? Or from forechest area to point of rump. Supposedly from "point of shoulder" to point of rump....is that the top of shoulder (withers) or where shoulder blade meets upper arm?

I would say, length of body is from withers to point of rump.

Length of body is measured from the point of shoulder (where the upper arm meets the lower part of the shoulder blade) to the point of rump.

"Proportion--Short-coupled; length from the point of the shoulder to the point of the rump is equal to or slightly longer than the distance from the withers to the ground. Distance from the elbow to the ground should be equal to one half of the height at the withers. The brisket should extend to the elbows, but not perceptibly deeper. The body must be of sufficient length to permit a straight, free and efficient stride; but the dog should never appear low and long or tall and leggy in outline. Substance--Substance and bone proportionate to the overall dog. Light, "weedy" individuals are definitely incorrect; equally objectionable are cloddy lumbering specimens. Labrador Retrievers shall be shown in working condition well-muscled and without excess fat."