Welcome to CC. I agree with your understanding of Scripture/GW. I have sponsored several threads including the Kerygma/GRFS, in which I explain the difference between the Gospel/kerygma and secondary doctrines as follows:
The distinction between kerygma and didache involves a difference in content and purpose. The kerygma proclaims GRFS, which calls for repentance and acceptance of Jesus as Lord, which is an all or nothing decision that occurs at one moment in time. The didache teaches God’s will regarding how saints or those who have been saved should live in order to be a good witness for Christ, which involves learning more of God’s Word throughout one’s lifetime.
A passage teaching this truth is Colossians 2:6-7: “Just as you received Christ Jesus as Lord [kerygma], continue to live in him, rooted and built up in him, strengthened in the faith as you were taught [didache].” There is no qualitative difference between faith that accepts God’s saving grace at conversion and faith that accepts God’s working grace while walking/living (EPH 2:8-10, 2CR 5:7, RM 1:17), but only a quantitative difference as each additional moment passes–and of course faith remains non-meritorious during the saint’s entire lifetime.
Notice that the kerygma/Gospel fulfills and supersedes OT revelation, but does not contradict its correct interpretation (HB 8:6-13). However, the NT revelation of GRFS will never become obsolete (PHP 2:9-11, RV 22:12-13). Thus, new revelations from God’s Holy Spirit will not contradict the Gospel, although they may express its truth in a different way or form, or else God would be inconsistent or tricky. There may be new wine skins, but no new wine (MT 19:17). Post-NT inspiration must be didachaic information regarding contemporary moral or political issues.
The kerygma/GRFS should be every Christian’s creed, and only belief in this crucial truth should be viewed as a test for orthodoxy or heresy. As Paul wrote in Romans 10:9, “If you declare with your mouth, “Jesus is Lord,” and believe in your heart that God raised him from the dead, you will be saved.” Conversely, judgments concerning a person’s spiritual orientation or ultimate destiny should not be made on the basis of didachaic or secondary doctrines. (If any judgment is made, it should begin with a self-examination per MT 7:1&5, 2CR 13:5-8).
A major reason many Christians throughout history have not manifested the love and unity of God’s Spirit (EPH 4:3) as well as they should is because of failure to realize this truth. If they did, it would free them to speak honestly and fellowship without becoming unduly upset about relatively minor issues. They would receive God’s blessing as peacemakers, who draw inclusive circles around people based on the kerygma rather than denominational lines between them due to didachaic differences. Jesus prayed for spiritual unity (cf. JN 17:20-23, “May they be one…”).