What an excellent summation of the Catholic Church's development. You left out one part, though... Christ gave the Deposit of Faith directly to His Apostles and that has been faithfully transmitted through the centuries. This is the Tradition (big "T") which illuminates Scripture. Just as Christ explained the Scripture which spoke of Him on the road to Emmaus so the Church has been given the commission to illuminate the Scriptures to those who have come since. (1 Tim 3:15).
Purgatory
"...the RC Church has been given itself the commission to illuminate, replace, contradict, supplement and supersede the Scriptures to those who have come since based on their Tradition (big T).
That's a lot closer to the truth, eh?