So, what physical proof do we have that the old covenant ended? Don't you know that if God didn't give us physical proof of what Jesus did, the church of today would be extremely legalistic and divided in two?
No, I don't think it would. Because the temple being destroyed isn't physical evidence of the end of the OC. It happened decades later, and was unrelated to the OC ending. The scriptures and the Holy Ghost and the testimony of the saints is our evidence. If someone wanted to believe in the OC without the new, there is plenty of "physical evidence", they could use (but no spiritual proof.) Israel survived the destruction and Rabbinical Judaism has flourished, hollow as it is, carrying on the Pharisees legacy.
I don't know why preterists always seem so afraid of Jews and temples. Christianity began just fine with Herods temple up. Everyone knows by now that Jews and Christians are not the same. And if you have concerns about the church being "divided"... we don't need a temple up for that.
Jerusalem was destroyed as a judgement for the rejection of Jesus- and a fulfillment of prophecy. It was a sign to Israel that they were wrong with God as a nation. (And yet they would not recognize it)
After the 70AD destruction, and the Jewish revolts that happened continued later- surely you're aware that Jerusalem became a "christian" city, where they vehemently opposed the rebuilding of the temple- yet they were conquered and the city taken by muslims- SURELY you DO NOT consider that to be "physical evidence" of the end of the new covenant and the beginning of a Muslim age...
While the 1st century Jews rejected the truth, ensuring the destruction of their city- it doesn't change the fact that JESUS- an ISRAELITE- fulfilled the OC.
So, while preterists will say that the jews from generations past ensured that their nation can never be redeemed, others might say that Jesus' fulfillment of the OC guarantees that Israel as a nation will eventually be redeemed.
I've not seen any convincing theology or understanding of prophecy from a preterist point of view... only a sick celebration and veneration of the slaughter of Jews.