A brief conversation with a Calvinist:
Ephesians 1:4-5; 11 and Romans 8:29 would seem to indicate fairly plainly that God does choose individually.
Additionally of interest, Romans 9:15-16. And Romans 9:11 when speaking about Jacob and Esau. As well, Acts 13:48 on those Gentiles APPOINTED for salvation.
Lastly, of the several references to the Book of Life only one mentions God taking away someones name and that is in Rev 22:19.
Since Scripture is clear that a true believer is kept secure by the power of God, sealed for the day of redemption (Ephesians 4:30), and of all those whom the Father has given to the Son, He will lose none of them (John 6:39). The Lord Jesus Christ proclaimed, “I give them eternal life, and they shall never perish; no one can snatch them out of my hand. My Father, who has given them to me, is greater than all; no one can snatch them out of my Father’s hand” (John 10:28-29b). Salvation is God’s work, not ours (Titus 3:5), and it is His power that keeps us.
Rev 22:19 is not referring to a true believer in the same way that Hebrew 6:4-8 does not refer to a true believer, but someone who is only playing at being a Christian or downright being a false believer.
To understand Paul’s message we need to understand Old Testament theology. Throughout the Old Testament, God’s promise to Abraham is held supreme. Throughout the Old Testament, Israel rebels from God and God vows to destroy all of Israel and leave a remnant. The idea is that the promise is allowed to be furthered through the people that God spares. John the Baptist has to counter the Calvinist election mentality of the Jews in Mathew 3 when they believe they are going to be saved by being the elect. John counters that God can fulfill His promise to Abraham by raising up sons from the rocks. John’s point is not that God knows His promises will be fulfilled through future omniscience (or some such nonsense), but that God is innovative and that is how He can fulfill promises.
Paul adopts both these concepts. In Romans 9, God grafts in the Gentiles to fulfill His promise to Abraham, and in Ephesians 1, God is intent on a remnant being chosen for Himself. None of these ideas carry the idea of “individual selection” as Paul points out in Romans 9:32-33 and John in Matthew 3:9. The predestined and chosen is this “remnant”, people get to opt into or out of this remnant based on how they live and what they believe.
Paul’s theology was very group dynamics orientated, because, like John, he was facing a Jewish theological movement that championed being Jewish above all else. A lot of Paul’s writings are dedicated to tearing down this Jewish superiority complex, thus we have verses like Eph 3:6:
Eph 3:6 This mystery is that the Gentiles are fellow heirs, members of the same body, and partakers of the promise in Christ Jesus through the gospel.
We would be hard pressed to take your quotes by Paul and think he was talking about individuals. That is just not what he was arguing.