I have had sheltie babies put under an anaesthetic to have retained canines removed at 5 1/2 months and 6 months of age, routine here I am sure amongst sheltie breeders. I do not allow my vets to traumatise even adult cattle dogs by trying to look in ears if the dog is uncomfortable with it or going to fight him. Such dogs, usually with a grass seed in the ear, get sedated, then the sedation reversed once he's finished the job. So, just wondering, could that be done for a pup that age? I don't know small breeds.
Also, I do agree with t.pettet that it's the owner who should learn how to pluck hair, then it can be done gradually, but the breeder should have told this owner how to do it, surely? It's beside the point when the OP said there were signs of infection though. Poor little dog, what a terrible death, and such a short life.