I do not hesitate to admit that there is much to learn for all (self included) who desire to know the division of the Church and Israel. I want to share a brief reply to the article “The Church Age” because many still have not understood the implications of Galatians 3:14. The blessing of redemption (v 3) through Abraham does not come to the generality of Israel, but to believing Israel, first (remnant of Israel), then the believing Gentile (Rom 1:16), making "one fold" (John 10:16).
To be included in the Church, which is the Body of Christ, faith in Christ must precede presence with Christ, and I believe Jesus addressed this in John 10:29 when He spoke to Thomas saying, "because thou hast seen Me, thou hast believed: blessed are they that have not seen, and yet have believed."
The Lord Jesus was referring to believing in His resurrection, which presupposes belief in His incarnation (1 John 4:2, 3; 2 John 1:7), thus belief in these two events supplants the believer with salvation (Rom 10:9). The generality of Israel will not believe in the Lord Jesus and I believe the living unbelieving Jew who sees and believes in Christ during the Millennium is the one who is prophesied to become a "people of God" (Jer 31:31: Eze 36:27).
The Jews who believe before Jesus returns will be included with the Gentiles who believe (Church). To my present understanding, the Church is one fold comprised from believing Jews and Gentiles, which makes them “children of God”. The Millennium Jew (the living Jew who did not believe prior to seeing Christ), by way of the prophecies of Jeremiah and Ezekiel, will become the "people of God."
There is much debate concerning whether or not the Jer 31:31/Eze 36:27 prophecies are in reference to the Jews or to the Gentiles also. Presently, I believe that these prophecies are separate from the prophecy of Joel, which has already started since Acts 2 and applies to “all flesh” (v 17); and the above prophecies are still yet future and applies only to the Jews. To me, one clear differentiation is evidenced by how the entire chapter of Ezekiel 36 is distinctively referenced to Israel’s history, i.e. verse 28.
The Jer 31/Eze 36 prophecies will have been realized when unbelieving Israel (unbelieving Jews alive at the time of fulfillment) will be given His Spirit and finally come to faith in the Lord Jesus, same as it already has been done presently in believing Jews and Gentiles. The significant difference is what Jesus spoke of in John 20:29, in that the Millennium Jews will not believe until the Father puts His Spirit in them and they see Jesus.
This would mean there are two new covenants; the one in the present dispensation which is in the "blood of Christ" (Luke 22:20 et al), and the one in future Israel—both are “everlasting” and Christ is the mediator of both (1 Tim 2:5).
Again, I want to share that I realize that my present comprehension which I have been sharing concerning the concepts relating to Israel and the Church could be speculative and may not necessarily be accurate because Scripture is not openly clear concerning this subject, which is the situation concerning many Biblical doctrines. But the doctrines which are clear, esp. those which are salvation-essential, i.e. Romans 10:9, cannot be speculative but rather must be definite in concept and acceptance.
I will be eagerly awaiting replies and thanks ahead of time for those who do.
Much appreciation for these 'Church Age' articles. - 'Kingdom Now' and 'Replacement' theologies, in all of their past and present forms and packagings, have never been even remotely correct. Christians (the Church), whether Jew or Gentile, are not called to save the nations (let alone the entire world), but are called to preach the Gospel of Christ to sinners, saving them from hell. - You've also correctly identified the difference between unsaved 'natural' Israel, and the last-days Jewish Remnant of believers (144,000), who will reign with Yeshua at His coming and His Kingdom at the end of the age (after the tribulation) when He will rule the nations with a rod of iron from Mount Zion for a thousand years. - Well done Robert.