I can see your confusion when you continue to try to mash the LORD's doctrine for Israel with that of the body of Christ.
What do you think Peter is speaking about here in "bold"?:
"Peace be with you all that are in Christ Jesus" (1 Pet.5:14).
What John says in the following verse can only be speaking of those who are "in Christ," in the Body of Christ:
"And this is the record, that God hath given to us eternal life, and this life is in his Son" (1 Jn.5:11).
Do you really think that teaching applies to Israel?
The body of Christ does not have a High Priest. We have a Head.
The Lord Jesus is now in heaven as High Priest and is now making intercession for all the members of the Body of Christ (Heb.7:25; Ro.8:34).
Besides that, in the first part of 1 Corinthians Paul writes that his words in that epistle are addressed to all that in every place call upon the name of Jesus Christ our Lord
"Unto the church of God which is at Corinth, to them that are sanctified in Christ Jesus, called to be saints, with all that in every place call upon the name of Jesus Christ our Lord, both their's and our's" (1 Cor.1:2).
Of course those who received the Jewish epistles are included because they called upon the name of the Lord Jesus. And here is what Paul tells them:
"For by one Spirit are we all baptized into one body, whether we be Jews or Gentiles, whether we be bond or free; and have been all made to drink into one Spirit" (1 Cor.12:13).
All, not just some.
Paul certainly believed that all those who received the Jewish epistles are members of the Body as well as the authors of those epistles.
Your ideas come straight from the Acts 28 crowd and neither Sir Robert Anderson, J.C. O'Hair, or Cornelius Stam taught that only some of the Jewish believers living in the first century were members of the Body. And O'Hair said the following:
"Peter and James and ten other apostles are going to sit on twelve thrones and judge the twelve tribes of Israel. (Matthew 19:27 and 28). But I do not agree with Christians who say that the twelve apostles were not members of the Body of Christ...I make no such foolish statement...that these Epistles of Peter and James are not for this age...I use 1 Peter 3:18 in preaching the gospel of grace as frequently as I use any other verse" [emphasis added] (O'Hair, The Accuser of the Brethren and the Brethren Concerning Bullingerism).