You're off in your reading of that - Romans 9-11 is about what happened between Israel and God [and that, in light of "this mystery" God had kept hid in Himself] that the Gentiles are now being called without Israel being re-born as a redeemed nation first.
Towards that, the above passage you have cited, declares, not Paul's gospel, but the clear opportuniy Israel had had through the witness of those "beautiful feet" God had sent them. Paul is not describing himself.
In the verses I cited Paul said it is the gospel which he [we] preach. The verses you cite about Israel are not a difficulty for me, but I do not see how you can say that the gospel he presented in Romans 10:9-10 is not the gospel he preached. He said it was. That is enough for me.
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