Joanna Kerns, the ideal mother on ABC's Growing Pains, is moving furthur and furthur away from perfection. IN the NBC film "Daddy," she's a divorcee without confidence or desire for motherhood. The TV-movie she's now developing for herself "is based on the Ruth Snyder case in the '20s. She and her lover, a corset salesman, murdered her husband. In the original script, Ruth was portrayed as a poor victim of a bad marrige who couldn't get a divorce. I said, 'Look, we've all been in bad marriages, but we didn't murder our spouses.' We figured out a different angle and hope to be doing it in May. It's a very, very black comedy about one of the dumbest murders in history."
