Yet they both spoke the same language...?
Your letting traditions of men cloud your understanding... You fail to understand everyone does not have the same role in the kingdom! James had his role... Paul had his role... they did as they were commanded!
Paul said... Rom 11:25 For I do not want you, brethren, to be uninformed of this mystery--so that you will not be wise in your own estimation--that a partial hardening has happened to Israel until the fullness of the Gentiles has come in;
and so all Israel will be saved; :thumb:
You appear to be uninformed of this mystery! :think:

oly::sherlock:
Paul
Romans 11:25's "this mystery" is not Ephesians 3:4's "mystery of Christ."
Consider that you have perhaps confused promises because you have applied the reasoning of men "about" a thing.
Romans 11:26's "And so all Israel shall be saved" is not about Ephesians 3: 6's "promise."
Romans 11:26's "And so all Israel shall be saved" is, concerns that which Paul relates there is "as it is written."
No Mystery there "as it is written."
Don't believe me?
26. And so all Israel shall be saved:
as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob:
27.
For this is my covenant unto them, when I shall take away their sins.
That is a 2nd Advent event - Isaiah 59:
17. For he put on righteousness as a breastplate, and an helmet of salvation upon his head;
and he put on the garments of vengeance for clothing, and was clad with zeal as a cloak.
18.
According to their deeds, accordingly he will repay, fury to his adversaries, recompence to his enemies; to the islands he will repay recompence.
Not 70AD either:
19. So shall they fear the name of the LORD from the west, and his glory from the rising of the sun. When the enemy shall come in like a flood, the Spirit of the LORD shall lift up a standard
against him.
He wipes out their enemies...
20. And the Redeemer shall come
to Zion, and unto them that turn from transgression
in Jacob, saith the LORD.
21. As for me, this is my covenant
with them, saith the LORD; My spirit that is upon thee, and my words which I have put in thy mouth, shall not depart out of thy mouth,
nor out of the mouth of thy seed, nor out of the mouth of thy seed's seed, saith the LORD, from henceforth and for ever.
Jeremiah 31:
33. But this shall be the covenant that I will make
with the house of Israel; After those days, saith the LORD, I will put
my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
34. And they shall teach no more every man his neighbour, and every man his brother,
saying, Know the LORD: for they shall all know me, from the least of them unto the greatest of them,
saith the LORD: for I will forgive their iniquity, and I will remember their sin no more.
What is that - this "saying, Know the LORD"?
That is this - Deuteronomy 6:
4.
Hear, O Israel: The LORD our God is one LORD:
5. And thou shalt love the LORD thy God with all thine heart, and with all thy soul, and with all thy might.
6. And these words, which I command thee this day, shall be in thine heart:
7. And thou shalt teach them diligently unto thy children, and shalt talk of them when thou sittest in thine house, and when thou walkest by the way, and when thou liest down, and when thou risest up.
8. And thou shalt bind them for a sign upon thine hand, and they shall be as frontlets between thine eyes.
9. And thou shalt write them upon the posts of thy house, and on thy gates.
10. And it shall be, when the LORD thy God shall have brought thee into the land which he sware unto thy fathers, to Abraham, to Isaac, and to Jacob, to give thee great and goodly cities,
which
thou buildedst not,
11. And houses full of all good things,
which thou filledst not, and wells digged,
which thou diggedst not, vineyards and olive trees,
which thou plantedst not; when thou shalt have eaten and be full;
He is the One Who will do for them what they could not do; including enabling them to both know, and keep His Law; from the least of them (children) to the greatest of them (their wisest)
Get off track as to what Romans 11:25's "this mystery" is and you can get off track as to the rest.
Romans 11:25's "this mystery" is the issue that during this time of Israel's
Prophesied* hardening, God is doing something else - among the Gentiles, and "until the fulness of" what He is doing among the Gentiles "be come in."
*Psalm 37:
7. Rest in the LORD, and wait patiently for him: fret not thyself because of him who prospereth in his way, because of the man who bringeth wicked devices to pass.
8. Cease from anger, and forsake wrath: fret not thyself in any wise to do evil.
9. For evildoers
shall be cut off: but those that wait upon the LORD, they shall inherit
the earth.
10.
For yet a little while, and the wicked shall not be: yea, thou shalt diligently consider his place, and it shall not be.
11.
But the meek shall inherit the earth; and shall delight themselves in the abundance of peace.
12. The wicked plotteth against the just, and gnasheth upon him with his teeth.
13. The LORD shall laugh at him: for he seeth that his day is coming.