In THIS way ALL Israel will be saved

[Clare73]

I guess it depends on what your thoughts are regarding what Paul wrote about the situation with the Jews having had their hearts hardened.

Isreal's destiny is to be grafted back into the one olive tree, the church (Ro 11:17), IF (not "when") they do not persist in unbelief (Ro 11:23).

Also, in my mind, your comment regarding the estimated number of all human beings who will actually get saved seems off.
I don't have a picture in my mind of any kind of numbers or percentages I think will spend eternity with God, but I concider your numbers to be far from worthy of our God.
I'm not being critical or harsh. Perhaps the images your words created were exaggerated by a simple misunderstanding.
Nevertheless, I think what Jesus said and what Paul wrote makes it clear to me, as I now understand, that there will be an....exception in this case.
Paul admonished those Christians in his day not to think too highly of themselves. That God had blinded them to the Truth to their advantage. That He would make what looked wrong right.
He isn't finished with the Jews and He can and will do as He chooses.

 

[Der Alte]

Ro 11:​

23 If they [the Jews] do not continue in their unbelief, will be grafted in, for God has the power to graft them in again. 24 For if you were cut from what is by nature a wild olive tree, and grafted, contrary to nature, into a cultivated olive tree, how much more will these, the natural branches, be grafted back into their own olive tree. 25 Lest you be wise in your own sight, I do not want you to be unaware of this mystery, brothers a partial hardening has come upon Israel, until the fullness of the Gentiles has come in.​

Because of the Jews' unbelief in Jesus, a partial hardening was upon Israel. ...

Note: 23 If they [the Jews] do not continue in their unbelief, will be grafted in, for God has the power to graft them in again.​

The converse of this vs. "If they [the Jews] do continue in their unbelief, will NOT be grafted in." If it was engraved in stone that all Jews would not continue in their unbelief Paul would not have written this verse as conditional.​