I'm not the puppy expert, but I don't think that a tiny puppy who is used to being with its mother will enjoy being in the tub. I think that might even traumatize him. The breeder didn't tell you what to expect? I find that pretty shocking!
I know it has been suggested here that puppies might be calmer with a ticking clock to simulate the mother's heart beat.
One thing is certain, the doggy would have been better off staying at the breeder for at least one more week. Normally, the breeder should keep the pups with the mother and the litter until 8 weeks. You are going to have to socialize this doggy with everything so that he doesn't become fearful or aggressive.
Good luck. I know in the morning, there will be better advice.
