I agree that the early Church leaders took their religious message to be allegorical or metaphorical. That was a hangover from Gnosticism: they distinguished between the intellectual elites and the initiates who had more simpleminded views. But as the Church grew more politically powerful, Gnosticism fell by the wayside, and the esoteric side of Christianity was purged or kept secret. Official Christianity came to identify itself with its exoteric message, with the simplistic, literalistic one that was meant for the uneducated hoi palloi.
No, I don't think a metaphorical reading of scripture is necessarily meaningless. Nor would I trust Paul for a nanosecond. In 1 Cor. 9, he says, "I have made myself a slave to everyone, to win as many as possible...I have become all things to all people so that by all possible means I might save some. I do all this for the sake of the gospel, that I may share in its blessings."
To take at face value the message of such a casuistic apologist seems to me foolhardy. Paul may have emphasized the concreteness of Jesus's resurrection just to appeal to that particular audience. Paul even lays out the Gnostic elitism, the intellectual hierarchy including those who have spiritual and mere natural understandings. How could Jesus have risen physically from the dead if Paul says that flesh can't enter the kingdom of God? No, Paul says it's a "spiritual body" that resurrects. Doesn't sound that literalistic to me.
This is such a canard about Christians dying for their religious beliefs. The number of martyrs were exaggerated, and we have no idea, regarding the Christians that were killed, why exactly they were killed or whether renouncing their beliefs would have saved them.