I know the slander on the part of those who say that they are Jews and are not, but are a synagogue of Satan.
This emphasizes that "true Jews" (i.e. God's chosen people) are Christians, those who have received Christ as their Lord and Savior. Anyone who denies this is not from God but belongs to Satan, the master deceiver.
These are the words of him who has the sharp two-edged sword
Hebrews 4:12-13. "For the word of God is alive and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart. Nothing in all creation is hidden from God's sight. Everything is uncovered and laid bare before the eyes of him to whom we must give account."
Jesus, who is the Word (John 1:1), searches and knows all things, and God the Father created all things through Jesus (1 Cor. 8:6). Jesus acts as God's divine agent through whom God reconciles all things to himself on earth and heaven (Col. 1:19). Jesus is the head of God's building, the church (Col. 1:18), and each member of the body lives through Christ's Spirit (1 Cor. 3:16). Jesus' prayer in John 17 shows us that God's plan is to have complete unity and oneness with man, having each person grow in the fullness of God (Eph. 1:23, 3:19).
so that they would eat food sacrificed to idols and practice fornication.
How do you understand this messaging compared to Paul's less strict teaching in 1 Corinthians 8:1-13?
To the one who conquers I will also give the morning star.
Jesus Christ is the Morning Star (22:16). Since ancient Babylon, Venus represented the morning star because it was visible at sunrise, and the morning star is symbolic for sovereignty, implying that overcomers will receive the sovereignty of Christ over nations (Trafton 44).
to rule them with an iron rod, as when clay pots are shattered
Overcomers will receive the authority and power that God designated to His Son, Jesus, in Psalm 2.
Whoever conquers will not be harmed by the second death
How does this fit in with the doctrine of "once saved, always saved"?
paradise of God
"Paradise" = paradeiso; literally means "garden"; connection between the Tree of Life in Genesis and Jesus as the True Vine in John 15, who came to give abundant life to those who receive Him (John 10:10). As we abide in Christ, we will bear fruit, which brings glory to God (John 15:8) and is a part of getting back to His original plan of man expressing God fully without any sin.