Been reading the threads for awhile now, wanted to jump in and add my theory.
For reference, I live near the area where she was found, and I am a mother in her 30s who has long blond hair and jogs in rural areas! Needless to say, this story has grabbed my attention.
At first I thought it was a crime of convenience or passion: a local creep, or truck driver passes by, or gets to know her patterns and snatches her up. I don't believe this to be the case, because typically those are the bodies found within a few miles of the disappearance raped and strangled.
I believe it was a ransom case from the get-go. And I don't believe her husband was the target. It is clear from all the dirt that has been dug up that Sherri and her husband weren't particularly wealthy.
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I also think someone on team 'SP' knows who is behind all of it, but cannot come forward because they purposely kept LE out of the loop, or don't want LE to know about their nefarious dealings. I would bet that the mastermind hired ****s to do the dirty work for a slice of the pie.
As for the branding, I think it was more about inflicting pain than anything else, but also a reminder to her and whomever the real ransom target was that they messed with the wrong people/person.