Not sure what you are trying to say here. Not all are saved, but some are.
First, the idea of eternal marriage just goes beyond Scripture. We know marriages last until one spouse dies. Then the other spouse is free to marry again. That's Scripture. We know that a marriage is not valid and must be dissolved if there is 'inappropriate contentea', the exception listed by Matthew, which is incest. We know that for two married heathens, if one becomes Christian and the other will not tolerate it, the Christian can remarry. And that because baptism is a form of death and rebirth, and marriage does not endure beyond death. The believer must stay married if the unbeliever consents to live peacefully with the believer.
The idea of ephemeral marriage seems lacking from the words of Jesus. He was pretty hard nosed about the permanence of marriage in this life. And nowhere did he say marriage was eternal. After all, whose wife would she be?
You say this without Scriptural evidence. Color me skeptical. It may be your belief. It may even be Orthodox belief, although I am not convinced that it really is Orthodox teaching beyond you and one author you refer to.
If this is Orthodox teaching, that 1.) a valid marriage can be dissolved by sin and 2.) that some marriages are eternal, it's two more reasons for me not to be Orthodox because I see those two things as anything but orthodox. The first is an error and the second is at best a wild speculation.