You have indeed made this an unnecessary dispute.
Ultimately, like knowing Jesus is the Christ, you'll just have to sort it out between yourself and the Holy Spirit if the NT is divinely ordained holy writ.
There are countless believers like myself who will testify that through use we can see that God indeed has set the NT aside as authoritative scriptural guidance and teaching and not just as the opinions of Christian scholars. Though Paul does make it a point to tell us when he's speaking from an educated opinion about a spiritual matter and when he's not. Which should show you there is a difference and Paul can tell the difference! Understand what I'm getting at?