Allow me to quote the following (from a non-Catholic source, btw):
Third Council of Carthage (A.D. 397). The Third Council of Carthage was not a general council but a regional council of African bishops, much under the influence of Augustine. The English text below is from Metzger.
Canon 24. Besides the canonical Scriptures, nothing shall be read in church under the name of divine Scriptures. Moreover, the canonical Scriptures are these: Genesis, Exodus, Leviticus, Numbers, Deuteronomy, Joshua the son of Nun, Judges, Ruth, the four books of the Kings, the two books of Chronicles, Job, the Psalms of David, five books of Solomon, the book of the Twelve [minor] Prophets, Isaiah, Jeremiah, Ezekiel, Daniel, Tobias, Judith, Esther, the two books of Ezra, and the two books of the Maccabees. The books of the New Testament: the Gospels, four books; the Acts of the Apostles, one book; the epistles of the apostle Paul, thirteen; of the same to the Hebrews, one epistle; of Peter, two; of John the apostle, three; of James, one; of Jude, one; the Revelation of John. Concerning the confirmation of this canon, the Church across the sea shall be consulted. On the anniversaries of martyrs, their acts shall also be read.
There are writings pointing to a synod at Hippo in 393 that made the first pronouncement of the canon, but I haven't been able to find the actual quote.
In answer to your specific questions:
History shows that it was a more gradual process than anything. But, face it, there were PLENTY of texts floating about in those days. Some of them might be genuine writings that were canonical, some of them might be authentic writings that were not canonical, some might be pseudographs. This Canon 24, quoted above, was more of an affirmation.
Well, not in of themselves...but we believe that the Holy Ghost worked through them.
Without such a list, how would we know that the Gospel of Thomas was not an inspired work? The Gnostics around today would have you believe it was...
I think you're closer here. You should remember that, particularly with the "New Testament" writings, there wasn't an organized "New Testament" prior to Jerome compiling the Vulgate in 382 AD. Originally, there were individual writings: e.g., St. Paul sent a letter to a church and that letter was circulated back and forth between churches. For example, the four gospels that we are familiar with were determined to be canoncial during the 2nd century (as documented by Iraneus)
But the fact remains that the writings were originally written as separate works and that those works were gradually accepted as inspired over a period of little more than 300 years. By whom? By the Catholic Church. And, in 393, they codified the list into what is known as the Canon. Again who? The Catholic Church.
So do I. But then it doesn't allow Catholics to make the fun argument that "if it wasn't for us, you wouldn't have a Bible." Which not all Catholics argue, and I must confess that I might think the same argument fun if I were a Catholic myself. Obviously, the Church played a huge role in preserving the Word of God for us today. Of course, God would have preserved His word one way or another. But it is worth our Protestant thanks to the Church for its work in preserving the Canon.