Sorry, I'm no expert on the forensics.
If the forensics are as cut and dried against the Ramseys as you indicate, why were they not indicted?
I can't stipulate as to all your forensic facts. Even if true, there can be exculpatory explanations that aren't considered by people whose minds are made up the Ramseys did it, or their son did and they covered up.
Hopefully the Grand Jury did the right thing, because the case was botched and the myriad of circumstances were confusing.
All I know about the forensics is that this is what is in the reports.
"...why were they not indicted..."
My only guess is good lawyers. All that evidence doesn't say who killed jonbenet, only that something doesn't add up. They can't convict on that, I don't think. DNA would be key, but if one of the Ramseys did it then it may never be revealed.