I agree, a direct translation wouldn't work. Maybe something like THE FRENCH LIEUTENANT'S WOMAN. Basically, instead of simply adapting the novel to film, the filmmakers decided to make it a love story within a love story. They invented two new characters, actors who are filming an adaptation of John Fowle's book while engaging in a love affair of their own. Thus, the movie shifts back and forth between the finished product (the movie of THE FRENCH LIEUTENANT'S WOMAN set in Victorian England) and the actors rehearsing their scenes, discussing the book/screenplay, and analyzing their own affair circa 1981.
They won't have to invent new characters for SUNDAY, but maybe they could tell both acts simultaneously, shifting back and forth from 1884 France to 1984 America. And since the actors in Act I play different characters in Act II, it'd be a nice echo of the past and present, so to speak. I don't know.
Salve, Regina, Mater misericordiae
Vita, dulcedo, et spes nostra
Salve, Salve Regina
Ad te clamamus exsules filii Eva
Ad te suspiramus, gementes et flentes
O clemens O pia