In addition to what eeeefarm has offered (and I would agree that if you have not you should make sure that he doesn't have an UTI), have you talked to his breeder about the issues? 8 wks is a bit early for Basenjis to be placed, especially in homes that are new to the breed. As a breeder, I find that most all Basenjis are not socially ready to leave their pack or dam (or other adults) until 10 to 12 wks. My pups are not placed until that age unless going to a have with experienced Basenji owners or homes with other dogs. Also at his age, I have found that when teething many times Basenji puppies will totally forget what housetraining is.
I disagree with the "bop" on the nose... "screaming" does the job BUT you need to do this each and every time and then ignore him. Also if he is not doing this with your husband, he also when this happens MUST ignore the pup. And by the way have you spoken with his breeder?