Interesting. You put alot of research into this.
It's pretty much game over if BK cut himself at the crime scenes and forensics finds his blood in or outside the house. Especially mixed in with the victim's blood or in the same room with the victims but really anywhere on the property.
Yes the defense could say he visited the King Rd property and left bodily evidence at that time but it would depend on many factors.
DNA on a knife sheath in a bed next to a victim is not the same as his fingerprint on a toilet handle for example. Any bodily evidence from him on/next to/mixed with, etc.. a victim is hard to defend. Blood is harder to account for then leaving a fingerprint on a door handle.
But then it could backfire. If he says he visited there but there is not one fingerprint, not one shread of evidence of his being there, isn't that suspicious?
His blood in his car or in his apartment can be explained as him bleeding from a nose bleed to any number of things but it would depend on how much blood, where is it located, is his defense of how he was bleeding believable?
Victim's blood in his car or in his apartment would be extremely difficult to defend. Even if he said he gave a ride to the victim or had them over to his apartment, still difficult to explain.
Then that plays into the prosecution narrative that BK knew some victims and stalked them. Also, forensics would expect to also find their fingerprints in his car and apartment. Again, that defense could backfire.
It's pretty clear that BK's blood on the King Rd property would be difficult for the defense, if not impossible to defend. A little easier if his blood is in his car or apartment. But pretty much game over if any victim's blood is found in his car or apartment.