So this pup got stepped on hard enough for blood to be coming out of it's mouth and nose, for it to stop breathing, for his heart to go faint, for his head to flop back and for him to have a seizure and the vet didn't recommend 24 hour care?
I'm not sure how much good diagnostics would do at this point, especially tonight because even if the pup had a diagnosis, I'm not sure they're be any real treatment, however, this pup needs to go to a 24 hour emergency hospital staffed with a vet immediately. It is nice for the breeder to come over but it really is not the time for that. The breeder is not a vet nor are the owners of this puppy. I know you'd like to see them go back to the vet, so this isn't helping any but I think that is the only thing we can recommend.
This pup's life is still in extreme danger and the best place for him to be is with a vet.