Thanks for your excellent information, perspective and attitude. You have answered questions I have had for years. I am still unclear though about the Tribulation saints’ need to maintain their faith, and about which covenant they are saved through, the Old or the New. Are you saying they are saved during that time by their faith in God through the Old Covenant system and that is why they must maintain it? If so then aren’t you saying there are two ways to be saved since the time of Christ? (The Old Covenant and the New Covenant?)
Ever since the Fall of Man there has only been one way to achieve salvation, and that’s through the substitutionary death of the Messiah (Genesis 3:15). Paul wrote that the Law was given to make man conscious of his sin, not to make him righteous (Romans 3:20).
Before the cross, man looked forward in faith that this would one day happen, but obedience to the provisions of what we call the Old Covenant was required as evidence of this faith. During the Church Age we look back in faith that it did happen, and obedience to the provisions of the Old Covenant is no longer required.
After the Church is gone man will again be required to give evidence of His faith by maintaining certain behavioral standards. Rev. 14:12 says salvation for Tribulation believers will require obedience to the commandments as well as remaining faithful to Jesus. And even after Israel receives the New Covenant they will still have to offer sacrifices in the Temple, maintain a Levitical priesthood, and keep certain Holy Days (Ezekiel 40-46). And Zechariah 14:16-19 tells us that even Gentiles will be held accountable to celebrate the Feast of Tabernacles. Clearly the post church provisions of the New Covenant will be different from those during the Church Age.
Viewed from the perspective of the entire Age of Man it makes more sense to see the Church as having a completely unique relationship with God rather than trying to reconcile Old vs. New Covenant practice for the days to come. But the one constant in all of this is that Jesus went to the cross to die for our sins and rose again. His death is the only provision God has ever made for our salvation (Acts 4:12).