What does it mean that an unbeliever is sanctified by their believing spouse? St. John Chrysostom seemed to think that it had to do mostly with intercourse not being unclean because of unbelief when the "two become one," but is there more to it than that?
I would recommend reading St. John Chrysostom’s commentary on these verses more carefully, as he has said a great deal about the subject:
For instance, he says:
Because here there is hope that the lost member may be saved through the marriage…
What then, is the [unbeliever] holy? Certainly not: for he said not, He is holy; but, “He is sanctified in his wife.” And this he said, not to signify that he is holy, but to deliver the woman as completely as possible from her fear and lead the man to desire the truth. For the uncleanness is not in the bodies wherein there is communion, but in the mind and the thoughts. And here follows the proof; namely, that if thou continuing unclean have offspring, the child, not being of thee alone, is of course unclean or half clean. But now it is not unclean. To which effect he adds, “else were your children unclean; but now are they holy;” that is, not unclean. But the Apostle calls them, “holy,” by the intensity of the expression again casting out the dread arising from that sort of suspicion.
As St. John points out, these words apply not to a believer who wishes to marry an unbeliever, but to a believer who is already married to an unbeliever. The unbeliever is not holy by virtue of remaining married to a believer; but there is hope of salvation for the unbeliever as long as the believer remains married to the unbeliever. Also, the believer is not made impure before God by joining in one flesh with the unbelieving spouse, and the children are not rendered impure before God by virtue of being born with one unbelieving parent.
St. John Crysostom must have have not remembered the words of God if your interpretation is correct.
"The TWO become ONE flesh". ONE flesh does not mean there is a clean half and a unclean half. It means there is exactly ONE flesh.
Also "The husbands body does not belong to him but also to his wife, and the wife's body does not belong to her, but also to her husband".
The scriptures clearly point out that in marriage, the believer can save the unbeliever.
End of story.
It does not state "already married" or "married before" etc. This is where going OFF sola scriptura bends and twists the written scriptures.
If you read through it, and ignore what men say about it who lived centuries after it was recorded, its really pretty simple.
The Orthodox ceremony of Matrimony speaks of becoming ONE flesh too. The crowns of martyrs are put on, signifying the death of the individual and unionization of the two. This is based on the scriptures.