PAUL WILLIAMS The once-ubiquitous songwriter returns to stage, screen—and Capitol Hill Paul Williams became wildly successful for penning romantic 1970s hits including “We’ve Only Just Begun,” “An Old Fashioned Love Song” and “Evergreen.” But behind the scenes Paul Williams battled demons of addiction. “I did 48 Tonight shows,” he says. “I remember six.” Goodbye, Johnny Carson; hello, Betty Ford. Today, more than 20 years clean...