This is a really tough situation, Dave Marsteller, because the problem ultimately boils down to superstition, irrational belief systems, and magical thinking.
I feel keenly for both of your students. The young man who got dumped is surely suffering. If I knew him, I’d validate his pain and reassure him that what happened is no reflection on him. Nothing about him or his actions could have changed the outcome. His worth as a person and as a romantic partner have nothing to do with this sad situation.
As for the other boy? He’s infected with self loathing and internalized homophobia. He’s bought into magical thinking that is demonstrably and empirically not true. If he’s not attracted to women, then data indicates that no amount of church going, prayer, or dating women is going to change that.
He’s setting himself up for heartbreak, and(not just incidentally) setting up some young women for heartbreak.
He needs to know what the facts are. He needs to know that if he doesn’t experience significant sexual attraction to women now, then he’s very unlikely ever to experience sexual attraction to women. He needs to know that a series of Christian men who once publicly claimed to have changed their sexual orientation with God’s help (including the founder of Exodus International) have since admitted that they were lying and have apologized for it.
He also needs to know that plenty of accepting and affirming Christian denominations will welcome him into their congregations and embrace him and his innate sexuality without judgement or equivocation.
How to get him this information?
I wish I knew.