You sound like a vet, very knowledgable. I thought I saw a site recently where they raised cats that looked like yours, in CA. I think they said Ocicat so it's probably a different breed.
"Ocicat so it's probably a different breed" Ocicats have 100% domestic cat blood but are selectively bred to get the spots. Bengals have varying amounts fo Asian Leopad Cat blood in them. Savannah Cats are another hybrid bred by using domestic cats bred to African Servals. This is Niko, an African Serval:

And this is Luca, a Savannah Cat who is 50% serval and 50% domestic cat:
