ROME — From sold-out screenings in Venice and Naples to standing ovations in Los Angeles, the documentary “Nino, 18 Days” has turned one of Italy’s most beloved singers into a study of a father seen, at last, through his son’s eyes. We spoke to film-maker Toni D’Angelo, known until now for hard urban thrillers like Falchi and Calibro 9, who told us the title comes from the 18 days he spent waiting at home as a new born while his father, Nino D’Angelo, performed on stage in Palermo. That gap became the spine of the film. Along the way he uncovered the man behind the Neapolitan myth, the depression that followed his grandmother’s death, the gunshots through the window that forced the family to flee Naples after a Camorra extortion threat, and the long migration that took his father from San Pietro a Patierno all the way to Rome.