A "Christian Martyr" is a person who is tortured and killed for the sake of his Christian faith. Tennessee Williams mockingly uses the same term to describe Amanda's prospective subscribers of her magazine in Scs.3 and 4 who suffer minor ailments to do with their sinus and kidney.
In Sc.7 the silly joke about 'Moses in the dark' is meant to ridicule Moses the great leader whom God used to split open the Red Sea but is powerless at the time of the power failure in Amanda's apartment.
A little later there is a mocking reference to 'the church of the Heavenly Rest' which was struck by lightning and burnt down as punishment for the sins of its congregation members.
Tennessee Willaims seems to say that religion cannot provide 'Heavenly Rest" in times of desperate poverty.
The social context of the play is America in the 193os. The family is struggling for survival-in Sc.4 they are not able to buy butter by paying cash. They are dependent on the sole bread winner Tom who plans to run away from home like his father.
Religion, especially organised religion isn't of much comfort or use in such a desperate situation. The few but striking instances of religious references emphasise Tennessee Williams' ironic and mocking attitude towards religion.
In Sc1 there is no reference to church going or a church service on a Sunday-only how Amanda entertained 17 gentlemen callers.
In Sc.4.The church bell is an important symbol which highlights how puny and insignificant and helpless drunken Tom is in contrast to "the Almighty."
A little later the stage direction reads: MUSIC UNDER: "AVE MARIA" to ironically contrast the Virgin Mother of Christ who symbolises absolute devotion unlike Amanda who is 'devoted' to Tom so that he doesn't abandon the family.
Similarly in Sc.5. as soon as Tom tells Amanda that he has invited "a gentleman caller" home the stage direction reads: "THE ANNUNCIATION IS CELEBRATED WITH MUSIC." The Annunciation is a church festival celebrated on March25th to mark the angel Gariel's announcement to the Virgin Mary that she will give birth to Jesus Christ the Saviour of mankind. Ironically, Jim the gentleman caller is no Jesus Christ- he only flatters to deceive.