REUTERS/Fred ProuserThe legal brawl between billionaire Leon Black and a law firm that’s represented three women who’ve accused him of sexual assault is growing vicious—with Black suing the accusers’ counsel just days after they claimed the mogul sicced private eyes on one plaintiff and her family.Last month, a woman using the pseudonym Jane Doe filed a shocking lawsuit claiming the 72-year-old investor violently raped her in 2002 at sex-trafficker Jeffrey Epstein’s New York townhouse. Doe alleg