Many Reformed theologians, like theologians in general, have believed in a future for national Israel. The difference between their biblical outlook and what goes around in dispensationalist/futurist/rapturist circles is considerable.
Dispensationalists believe that the modern state of Israel is prophetically significant in spite of the fact that they exhibit no true faith towards the triune God of the Bible. Dispensationalists believe we are the terminal generation because of what happened 1948 -- a purely political action -- not because any true faith is exhibited in the nation
The Bible, on the other hand, teaches that blessing is predicated on faith, true faith in the God of Abraham, and the Savior of mankind, the Lord Jesus Christ. National repentance will be exhibited in Israel before the return of Christ for His own. That may be in the near future, or, more likely, it may still be many generations away. Of course this is true of all the nations, not just Israel.
It is necessary that Israel does not exhibit true faith in the triune God until the time of the gentiles ends. If Israel comes to Christ before the rapture, I will admit that I was wrong.
“National repentance will be exhibited in Israel before the return of Christ for His own.”
Now we get into the problematic situation of one groups belief being predicated on another groups dissolution on their religion. All major Abrahamic faiths have a version of this.
It can present a problem of coexistence, unless you arrive at a different interpretation. In other words, can you be faithful to the Gospel and believe Jews have a sacred right to their practices without compromise?
For Jews, it was the Pagan/Amalaks and others who are no longer a factor, and today there is an extreme faction who refuse to acknowledge Israel’s creation, as they believe it contradicts the notion of a Biblical Israel, which they believe requires the building of the Third Temple, which will either usher in a Messiah, or be delivered by the Messiah. Jesus is in no way shape or form a Messiach figure for Torah observant Jews.
Finally, you can support Israel and Jews as brothers and sisters without needing to cite scriptural reasons for it. The biblical argument rarely wins unless it’s an argument amongst others who already subscribe to that doctrine. For example, none of us could give a hoot what the Koran says...although it too does speak of G-D’s covenant with the Jews.