God's Grace is God's Blood.
The Cross is the revelation of God's reconciliation. John 3:16
Salvation is offered by God's mercy, and never is it attained by self effort, that includes lifestyle, law keeping, or commandment keeping.
All who go to the Cross , repenting of unbelief, are washed in the Blood of Jesus, and have God's reconciliation. "Justification by faith".
This is the "Gift of Salvation".
John 14:6
From the Kingdom Gospel standpoint, the flesh and blood of Jesus are His words and His life's work. Jesus used the the bread and wine as metaphors and ratified the covenant He was giving to the men His Father gave to Him; by accepting these tokens, the 11 signed onto this covenant, and later agreed to take this Gospel to the nations where the lost sheep of the house of Israel had been scattered, Matthew 28:19-20. The message to the circumcision never changed.
The reason Jesus died is all the way back in Genesis, where the seed of the woman crushes the serpent's head. When Jesus Resurrected, He defeated Death and the serpent... which seem to be one and the same. This is that Death riding the pale horse of Revelation.
From the Kingdom Gospel standpoint, Peter's Gospel tells us to repent and believe the Kingdom Gospel. This is the same thing John the baptizer had done minus the Gospel itself... and since there was no unbelief of which to repent, the doctrine of repentence was telling the circumcision to change their minds back to when they believed what Moses had been given by God at Sinai. And of course we all know that Jesus says the Law will stand until Heaven and Earth pass away, i.o.w., the millennium. Jesus also tells the lost sheep of the house of Israel that His words will never pass away.
Two different gospels for two different people... shouldn't be hard to understand if you'd read one separate from the other... and then read the other. That's how it worked for me. I'd read nothing but Paul for years, until I could argue with the best of them... you're not even in the ballpark, sorry. And then I set Paul aside and read nothing but Matthew and John. I want the truth, and was willing to go for it, no matter what other people told me it would cost... including salvation--that's how bold those jurors were. But I have come to believe it's not one gospel, period. Because Jesus says He came only unto the lost sheep of the house of Israel... from there, He chose His 11 from Galilee. And He sent them to the same people He came unto. And since Jesus' words never pass away, we know that's where Jesus sent them in Matthew 28:16-20.
And apparently Paul went to everyone else including the southern half of the divided kingdom... which people notice and think that the Jews means the whole family of Jacob, which it doesn't since the kingdom is still divided today. In fact, technically... since Isaiah 65 and Jeremiah 19 both say Judah is broken and cannot be mended, which Jesus affirms in Matthew 21:33-44 when He says the Kingdom is taken from them and given to a nation bringing forth the fruits thereof... this is where Judah will get its people who sought God but weren't called by His name. Because it's not Israel of the north that gets replaced (they are still called by His name), it's Judah of the south... which will be replaced by the people called by another name, so Paul's right when he calls you spiritual Jews... but you're wrong in thinking that spiritual Israel includes the 10-tribes-called-Israel.
Am I making any sense to you, or am I expecting you to know the background material to these thoughts of mine?