[PennysMum]

With these other issues beginning to show up, I'd be a little suspicious of the breeder tbh. Are you really really sure that she's respectable-- visited the place, saw the dogs and their parents yourself, or had a very trustworthy recommendation from somebody else who had? AKC registration means nothing as far as how good the breeder and their facilities are-- and if the pup is crawling with parasites, it would worry me that she might not be being forthright with you. :/

Little squirmy white things could also be lice-- which are a lot easier to deal with than maggots. Fingers crossed that's all it is! If they aren't moving, white grain of rice looking things near puppy's back end could be tapeworm segments.