I don't think they have DNA back on all the people whose DNA they took. But there are RSOs (and others) who have DNA on file for one reason or another. So those people could be eliminated as suspects. Maybe this guy had DNA on file? And that is why he is not a suspect?
JMO but I think they do have the DNA from Somer (no way is something rushed and a priority going to take 8 weeks with FBI and NCIS involved. They have their own labs.) Maybe there is something about the perp (disease) that this guy doesn't have.
Re: The dogs
Human, I have a beagle, and with my neighbors boxers in mind, I don't think the result would be this big. These pups look big to me (for 8 weeks).
Beagle and some kind of large dog mix? No? They do not look like boxers at all to me. Beagle and German shepherd mix? I don't think they are a purebred.
I don't know about the killer not killing dogs, but killing humans. I don't know if the 2 are mutually exclusive. Any killers that we know that loved animals?