I like that, "cultural exchange". Whether we agree or not, we can get to know one another, no?
I apologize for the terminology "age of grace". I borrowed it from other posts making the assumption that "this age" is commonly seen as "the age of grace" by the people here. I made a mistake in such a broad generalization.
I do not see Paul's "we" as including myself and you. Rather, it included the Galatians that he was writing and addressing. Biblically, the world ("Kosmos") of Noah passed away in the flood. Then there was only what Jesus, Paul etc termed "this world/aion" and "the world/aion to come". The kosmos of Noah existed within the old aion. The old aion began in Genesis 2 and the forgiveness of sins imputed upon all ended it.
That world/aion had within it certain elements. There was the temple, where sacrifice was offered and had to be offered yearly. There were the leadership thereof, who determined who was worthy of the presence of God (in the "holy of holies") and how near they could come to it -- or whether they would be entirely exiled or killed. They earned righteousness through keeping the law in the flesh.
The flesh btw, was the weakness of the law itself. They believed what their eyes and ears witness per their ability to keep it and they believed their eyes and ears per their ability to even understand it. They believed that because they could clearly see that they had never slept with a woman outside a covenantal bond, for example, that they were innocent of adultery. They felt that that could justly stone adulterers therefore, and they did. That is, until the law was righteously interpreted by Jesus and their innocence questioned within their own consciences.
Anyhow, that world was entirely different than this one and the evidence of its' passing was the fall of the temple. When Jesus talked about that fall, the disciples understood that as the end of their world and asked him for signs leading up to it which he then gave them. Keep in mind though that those were signs leading up to the fall of the temple/the end of their world.
Paul breaks down in Galatians the allegory of two covenants. In Hebrews 8 he again talks about the coming covenant and writes "In the saying, New, He has made the first old. And the thing being made old and growing aged is near disappearing." (vs 13)
In Paul's day it was "near disappearing". And what was the evidence for the end? The fall of the temple.
Mat 27:50 And crying again with a loud voice, Jesus released His spirit.
Mat 27:51 And, behold! The veil of the temple was torn into two from above as far as below. And the earth quaked, and the rocks were sheared!
Mat 27:52 And the tombs were opened, and many bodies of the saints who had fallen asleep were raised.
Mat 27:53 And coming forth out of the tombs after His resurrection, they entered into the holy city and were revealed to many.
Mat 27:54 But the centurion and those with him guarding Jesus, seeing the earthquake and the things taking place, they feared exceedingly, saying, Truly this One was Son of God.
Isn't this indicative of timing? Or:
Mat 28:1 But late in the sabbaths, at the dawning into the first of the sabbaths, Mary the Magdalene and the other Mary came to gaze upon the grave.
Mat 28:2 And, behold! A great earthquake occurred! For descending from Heaven and coming near, an angel of the Lord rolled away the stone from the door and was sitting on it.
Act 16:25 And having prayed, toward midnight Paul and Silas praised God in a hymn. And the prisoners listened to them.
Act 16:26 And suddenly there was a great earthquake, so that the foundations of the jail were shaken. And immediately all the doors were opened, and all of the bonds were loosened.
Actually, when Jesus was naming the signs leading up to the fall of the temple, he listed:
Mat 24:7 For nation will be raised against nation, and kingdom against kingdom; and there will be famines and plagues and earthquakes against many places.
I think it is so important to consider the relevance of who is being addressed in any text. When Moses said "Let my people go" to the Pharaoh, no one assumes that is talking to us as well. Jesus talks often to his disciples and the texts say so, yet people assume that he is talking with them as well. And Paul's letters are "letters" with addressees. The "you" or "we" isn't us, but whomever he is writing. That doesn't mean that means nothing to us.
I agree with you that the unpardonability of the sin of blaspheming the holy spirit doesn't mean that the people not believing Jesus and burning in "Gehenna fire" would not be gathered to God as well.
Firstly, "Gehenna" was a literal place. It was the "Valley of Hinnom" just south of Jerusalem. It was a place where they burned trash and bodies that they did not consider righteous enough for proper burial. The place had been considered unclean by the Jews since it had been used as a place to offer human sacrifice to the god Baal. The bodies burning in the heap were slow burning and warm - enabling the breeding of maggots, hence "where the worm dieth not". Jerusalem absolutely mirrored that place after the Roman seige - read the history.
They would not have another chance to believe that Jesus is Savior rather than the temple system because that system would be cast down, and many people would suffer in the "flames of Gehenna". However:
Hos 1:7 And I will have mercy on the house of Judah and will save them by Jehovah their God. And I will not save them by bow or by sword, or by battle, by horses, or by horsemen.
1Co 3:15 If the work of anyone shall be consumed, he shall suffer loss; but he will be saved, but so as through fire.
What happened with Israel was a revelation of the solution for a human-wide problem: sin and the death which resulted in it.