I am still not getting it. You believe that the Gentiles are partakers with the Jews of all the promises made to Israel, but you still have trouble allowing that the Jews and Gentiles who are the partakers of these promises are "the Israel of God"? You seem to want to retain a strictly ethnic definition of "Israel"—but this is entirely artificial, since there never was a time in history when all of Israel were Jewish by blood. There were always proselytes, who had no ancestry from the patriarchs, but who, after being circumcised, were included in Israel. This is because "Israel" was never a strictly racial designation. All of Jacob's sons married Gentile women, which means that every descendant of theirs was at least 50% Gentile by blood. It is obvious from both testaments that bloodline has never been the primary concern in defining who is a "child of Abraham" (God could turn stones into them!) nor in deciding who is included in "Israel."
A racially-mixed multitude left Egypt and and became "Israel" by entering into the covenant at Sinai. Later, Gentile bondservants and "strangers within the land" were able to be a part of Israel, simply by accepting the terms of the Old Covenant. In fact, in the days of Esther, many of the Persians also "became Jews" (Esther 8:17). They had no pedigree of descent from Abraham, Isaac and Jacob, but that did not prevent them from becoming part of Israel.
Today, when a Gentile becomes part of Israel, it is not by accepting the terms of the Old Covenant, but by accepting the terms of the New Covenant that God made with Israel (the remnant) in the upper room. Instead of circumcision, the terms require that one becomes a new creation in Christ (Gal.6:15). If a Gentile could be part of Israel under the terms of the Old Covenant, why do you object to Paul including Gentiles in Israel under the terms of the New Covenant? "Israel" has always included ethnic Gentiles as well as ethnic Jews.
You acknowledge the obvious fact that Romans 9:6 excludes some Jews from what Paul is calling "Israel," because we can all see that Paul is only including the believers among them (the remnant) under that label. Thus, you recognize that an actual Jew (as in Old Testament times, so also now) can be excluded from the people of Israel by his betrayal of the Covenant, but you inconsistently want to deny that a Gentile who embraces the Covenant can be included in Israel (see Isaiah 56:6-8).
Strangely, you allow the Gentile believers to be recognized as "Abraham's seed, and heirs according to the promise"(Gal.3:29), and to be "the [true] circumcision" (Phil.3:3) and to be "the children of promise"(Gal.4:28), and even "a chosen race, a holy nation, and a royal priesthood" (1 Pet.2:9—all terms used in the Old Testament distinctly of Israel)—but you do not extend to them the right of being called "Israel." If you are right, then, since Christ came, we are in the only period of history during which Gentiles cannot be a part of Israel. Are you aware that this means that privileges for Gentiles under the New Covenant are less than they were under the Old Covenant—and we are kept more "at arm's length" from Israel today, after "the middle wall of partition has been broken down," and "we who were afar off have been brought near," and have been made "one new" man with them? This is bizarre theology, my brother!
You hang much on Romans 11:12, 15 and 28. The fact that you bring them up tells me that you did not read the links I gave you, where I discussed this material. Suffice it to say that there is a grammatical similarity in all three of these verses. That similarity is the repetition of the words "their" or "they" in ambiguous phrases. For example, you used parentheses to give your interpretation of verse 28 as follows:
"concerning the gospel they (the Jews) are enemies (true), but concerning the election they (the Jews) are beloved for the sake of the fathers."
I imagine it has never crossed your mind that Paul's meaning might as easily be:
"concerning the gospel they (the Jews) are enemies, but (by contrast) concerning the election they ("the election"—that is the remnant of verse 7) are beloved for the sake of the fathers."
I know of no grammatical rule that would make the second "they" refer to anyone other than the nearest nominal antecedent ("the election"). It seems only to be an assumption of dispensationalism to make both occurrences of "they" refer to the same group, despite the fact that a new noun has been introduced between them.
It is similar with verses 12 and 15. Consider the possibility of the following meanings (in constructions similar to that in v.28):
Verse 12. Now if their (the Jews') fall is riches for the world, and their failure riches for the Gentiles, how much more their (the Gentiles') fullness!
Verse 15. For if their (the Jews') being cast away is the reconciling of the world, what will their (the world's) acceptance be but life from the dead?
Not only is this alternative interpretation reasonable, but it is more likely than yours for a number of reasons:
1. This interpretation follows the general rule of having the pronoun refer to the nearest antecedent noun;
2. Apart from these verses, Paul has not mentioned anywhere that he expects a national restoration of ethnic Israel, and yet he speaks of the results ("their fulness" and "their acceptance") as a given, as if his readers already knew of it. He has discussed the inclusion of the Gentiles earlier in this discussion, but he has not previously, either in this discussion, nor in any of his writings, ever hinted at a belief in a national conversion of ethnic Israel;
3. Paul, elsewhere in the same chapter speaks (as in verse 12) of the "fulness of the Gentiles" (v.25). Yet, he never mentions the "fulness of the Jews" in any of his writings.
4. Similarly, Paul (in Romans and elsewhere) speaks (as in v.15) of the "acceptance" of the Church and of believing Gentiles (Rom.15:7/Eph.1:6), but he never, in this discussion nor any other, makes reference to the "acceptance" of Jews as a category separate from the Church.
If this interpretation seems unnatural, one must ask if this unnaturalness is due only to the manner in which we have been taught to hear these verses. I gave the following example in one of the posts I had linked for you:
I expect that you will simply say that this interpretation seems (to you) "forced"—which is a subjective way of saying "I am not comfortable with it." But consider this...these verses (along with verse 25) are the only verses in all of Romans 9-11 (in fact, in all the New Testament!) that can conceivably be used to sound like possible predictions of a future restoration of Israel in the end times. If this was an actual belief that Paul held, is it not strange that he never mentioned it in any of his writings (nor in this particular discussion) other than in these three verses, which are, indisputably, ambiguous? Is it not equally clear that these same verses, seen the way I am suggesting, simply presuppose a knowledge of the points that Paul has been making through the whole discussion, and not of some otherwise-unmentioned eschatological conversion of the Jewish race? I honestly think you need to go back to the drawing board with your interpretation of Romans 11.As for the construction [of Romans 11:12] I mentioned that I preferred, suppose we read a sentence like the following in a discussion about Egypt:
"If God got so much Glory out of their destruction, via the ten plagues, and if their destruction proved to be the salvation of Israel, what glory might God expect to receive by His bringing them into their promised land?"
Such a sentence has a structure very like the one we are considering in Romans 11. Because we know the underlying story to which the writer is alluding, we would easily recognise that the first two instances of "their" refer to the Egyptians, but that the final "their" is clearly a reference to Israel. The greater ambiguity of Paul's statement is only due to less familiarity with the underlying "story" that informed his statements.