That’s complicated. I believe it’s much simpler.
If I understand you correctly, you are dividing things based on what they are called. Something referred to by different names can be the same thing but things that are different cannot be called by the same name or that would create confusion. For example, Jesus and Satan can be referred to by many different names but both cannot be referred to by the same name.
I see grace, the church, the faith and the body of Christ the same way, they can be called by different names and still be the same.
Here Paul uses church and body interchangeably.
Eph. 5:23 For the husband is the head of the wife, as Christ also is the head of the church, He Himself being the Savior of the body.
Here Paul calls the church the church of God.
1 Cor. 1:2 To the church of God which is at Corinth, to those who have been sanctified in Christ Jesus,
Here Paul says he persecuted the church of God before his conversion. If it’s not the same church as the one in 1 Corinthians 1, then this is a confusing statement.
1 Cor. 15:9 For I am the least of the apostles, and not fit to be called an apostle, because I persecuted the church of God.
Also, Paul says people were in Christ before him.
Rom. 16:7 Greet Andronicus and Junias, my kinsmen and my fellow prisoners, who are outstanding among the apostles, who also were in Christ before me.
What established the church and the body? The same thing, Christ’s death, burial and resurrection.
Eph. 2:16and might reconcile them both in one body to God through the cross,
Acts 20:28.. to shepherd the church of God which He purchased with His own blood.
Paul said he was a minister of the new covenant.
2 Cor. 3:6 who has made us sufficient to be ministers of a new covenant, not of the letter but of the Spirit. For the letter kills, but the Spirit gives life.
He said communion is blood of the new covenant.
1 Cor. 11: 25 In the same way also he took the cup, after supper, saying, "This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me."
It is simpler and makes more sense to me that the church and body were established by Jesus’ sacrifice and on Pentecost 3,000 plus souls were added to the church. The Jews were to hear the gospel first and they did. Then the Gentiles were later grafted in once they heard the same good news, Jesus is savior of us all.