Jimmy Kimmel returned to his ABC late night show Monday night and showed off son Billy, after taking off the previous week following Billy’s latest heart surgery. “Look, he’s fine everybody!” Kimmel crowed. Kimmel thanked last week’s guest hosts and the doctors and nurses at Children’s Hospital in LA who treat children from all income levels, “whose health is especially threatened right now because of something you probably never heard of called CHIP,” the Children’s…