As far as I can tell, he doesn't even believe that Jesus is God's only begotten Son. We might as well be debating with an atheist. It would take a month of Sundays to disabuse him of all his errors and delusions. I just don't have that kinda time, especially now. Do you?
The fact that he rejects the Apostles' Creed (or at least the bulk of it) alone speaks for itself. It's just about the most widely accepted statement of faith, so his rejection thereof is proof that he preaches 'another gospel', if any further proof were needed.
Speaking for myself, I twigged that much long ago, & I suspect every other true believer has too.