My money is on maturing and jockeying for top dog position, but that wouldn't explain the not wanting to eat. While the idea of humans being the alpha has been pretty thoroughly debunked, most certainly you need to enforce that aggression isn't okay.
But first, you need to make sure nothing medical is going on. Could picking him up be hurting him? Basenji do have hip dysplasia and they can suffer from Panosteitis. Though rare, IPSID... an inflammatory bowel disease, is also a concern. Have you talked to his breeder?