With regard to the Petros/Petras question, it is, of course, very valuable to move back to the Aramaic, where we find that Peter’s name, “Kephas,” as he is referred to throughout the book of Acts and in many of St. Paul’s epistles, means “a large rock” - that is, “Petra” in Greek.
From this, along with the fact that the word “petros” was not in use in the Greek language at the time of Matthew, it is easy to see that Jesus’ new name for Simon, which we pronounce as “Peter” in English, means “a large rock” and that Jesus, indeed, intended to ordain Peter as head of His Church, as our Catholic Church history also confirms.
We can also quite profitably move forward to the English as it is used in modern times, by simply reversing the problem and asking ourselves, “What is the name given to little girls, when we wish to name them after the Apostle Peter?”
The name given to these little girls (at least, in larger towns and in cities) is “Petra.” Further, little Petra knows, usually by the time she is three years old, that the reason she is called “Petra” is that “Peter” is a boy’s name - this little three year old girl understands something very important here, which is that Petra is the girl’s name, and Peter is the boy’s name, but that both names are the same name, and that, when a boy or man is named after a Petra, he has to be called “Peter,” just as when a girl or woman is named after a Peter, she has to be called “Petra.”