THE Pelham Picture House’s third annual gala, held earlier this month at the Hilton Rye Town in Rye, brought the historic theater another step and half a million dollars closer to fulfilling its mission of becoming a hub for independent film in southern Westchester. The goal of the event, said Jennifer S. Christman, the theater’s executive director, was to ensure a significant percentage of the capital needed for the Campaign for Renewal, which encompasses the restoration and expansion of the theater.