I'm so sorry you've had to deal with this. People who cut corners with breeding, pump out as many puppies as possible, and talk a smooth game to convince buyers they're reputable are depressingly common, and have been especially bad lately due to demand for puppies (and pets in general) spiking due to lockdowns. Don't be too hard on yourself - these are practiced con artist who make their livelihood tricking people.
At this point I'd call the vet back about him not eating. Baby puppies can decline incredibly quickly when they're sick. Like human babies, they're incredibly prone to dehydration and hypoglycemia, and them not eating or drinking enough is a much bigger and scarier problem than it is for adult dogs. Your puppy may be eating and drinking enough for your vet to be satisfied he's doing well, but that needs to be a call made by a trained veterinary professional who, if necessary, can physically examine him. Good luck, and keep us updated!
At this point I'd call the vet back about him not eating. Baby puppies can decline incredibly quickly when they're sick. Like human babies, they're incredibly prone to dehydration and hypoglycemia, and them not eating or drinking enough is a much bigger and scarier problem than it is for adult dogs. Your puppy may be eating and drinking enough for your vet to be satisfied he's doing well, but that needs to be a call made by a trained veterinary professional who, if necessary, can physically examine him. Good luck, and keep us updated!