To say that Paul's epistles are where "we should find God's Plan, Purpose, And Directions For The Body Of Christ, Under GRACE?: "
sets up this apostle as the basis upon which the rest must be judged including Christ's own words. That is a dangerous thing which can lead to false teaching. It also flies against Paul's own warnings to the Corinthians. He wanted them and us to focus on Christ and him crucified. That is found in the OT which points to Him, the Gospels which reveal His life and the Epistles which are the history of His good news being spread.
He made this point clear in the passage you first quoted:
“All Scripture Is Given By Inspiration Of God, and is
profitable for doctrine, for reproof, for correction, for
instruction in righteousness” (II Tim. 3:16).
Lets turn to all Scripture.
