THE CHURCH IS THE PILLAR OF WHAT- the Truth.
Yes and what is the design of a Pillar? Obviously to hold something up- right? Well if the Church is the pillar of the truth- then we ask : what is the truth? Jesus answers this question in John 17- “Thy word is truth.”
And he also says, “I am the truth.” And he also says he is the Word. So “Thy word is truth” could easily mean, “I am the truth.” On the other hand, “thy word is truth” could simply mean that everything God says is true. You see the kinds of interpretive issues passages can have when there’s no authority clearly distinguishing the correct meaning? Though that little fizzle over that verse is nothing compared to the major difficulties over doctrine that consume Protestantism. Those doctrinal differences are so large that thousands of denominations have resulted. They aren’t small enough that people feel they can be part of the same denomination in spite of the differences- the church fragments into many pieces. The Early Church did not endure such division. There were heretics, but they were proclaimed heretics and separated from the Body by excommunication throughout Early Church history. They were one body. They maintained that unity through a strict adherence to the teachings of the bishops, who in turn took their teaching from the bishops before them, and so on back to the first bishops, the original apostles. Ignatius and Irenaeus, among others, wrote very strongly about that, and Ignatius was one of the Apostle John’s own disciples. The Protestants threw submission to the tradition passed on by the bishop completely out the window when they left the Catholic Church.
As to pillars holding up the Word of God, I’d agree with that, and I’d say that Sacred Tradition is
part of the words of God that this pillar holds up. It was throughout the history of the Early Church- the Bible canon was only settled in the late 5th century, and when it was settled, it was not the present day Protestant canon. Luther dumped books he didn’t agree with into an appendix, including Jude, Hebrews, Revelation and several others that almost all Protestants today accept. Later generations of Protestants put those books back, but they didn’t reintroduce the Deuterocanonical books, which were part of the Bible settled on in the councils of Rome, Carthage and Hippo.
In any case, I agree with you that the word of God is truth and therefore is a key part of what the Church supports, but that word, I believe, extends beyond the Bible.
So why do Catholics not simply hold up the word of God? Why all the inventions?
We do hold up the word of God. More of it than Protestants do, tragically. Protestants removed multiple books from the Bible, and they also removed Sacred Tradition, both of which are the words or teaching of God.
That is tragic. And I used to have been part of that, because I once was Protestant as well

. Which is great, as it holds up so much of God’s teaching, but tragically it has a lot of gaps.
The “inventions” go straight back to the apostles. Many of them are in the Bible and only reinterpretations of the Bible by Protestant Reformers got rid of them, or the removal of books from the Bible that previously had been included.
I may respond to the rest later.