Here are the facts:
The 2 words
petros and
petra are different, though they come from the same root.
Petros is a movable stone as in the sentence: 'leave no stone unturned' That is the word used of Peter in My 16.18. You are
petros
Petra is a huge rock, cliff, boulder or similar.
The meanings and significances are totally different, and Jesus could not have meant that Peter was any kind of rock to build His church upon.
You say that the link to Isaiah is improbable. That cannot be correct because at least, we have: Lu 20:17 And he beheld them, and said, What is this then that is written, The stone which the builders rejected, the same is become the head of the corner?
Which stone was that? Peter? Totally unbelievable. This is Jesus Himself, not His disciple. I think you can see that.
Peter himself disavows the claim, 3 times in the following passage:
1Pe 2:6 Wherefore also it is contained in the scripture, Behold, I lay in Sion
a chief corner stone, elect, precious: and he that believeth on him shall not be confounded.
1Pe 2:7 Unto you therefore which believe he is precious: but unto them which be disobedient,
the stone which the builders disallowed, the same is made the head of the corner,
1Pe 2:8
And a stone of stumbling, and a rock of offence, even to them which stumble at the word, being disobedient: whereunto also they were appointed.
It shouldn't be too difficult to see that he is talking about Jesus, not himself. And if he himself thought so, who are we to say any different?
But to return to your improbability claim.
You must surely know that scripture is an incredibly allusive book, and there are allusions to other parts of scripture everywhere. I can't go into that in detail now, but suffer it to be so for a little while. Trust me on this one, and if you don't, look at the marginal references in your own Bible, and you will get some idea of just how many there are.
The most important allusions are those where the exact same few words are used, and this is one of them as I pointed out above. Here it is again, and I'm sure that you are able to see the correctness of what I'm saying.
Isa 38.9 ¶ The writing of Hezekiah king of Judah, when he had been sick, and was recovered of his sickness:
10 I said in the cutting off of my days, I shall go to
the gates of the grave: I am deprived of the residue of my years.
In Hebrew, the grave = hell = sheol
So when Jesus says:
Mt 16:18 And I say also unto thee, That thou art Peter, and upon this rock I will build my church; and
the gates of hell shall not prevail against it.
He is referring to the two passages above.
Hezekiah had been sick unto death. He went to
the gates of hell (=the grave), but without going through them.
Jesus on the other hand, went
through the gates of hell (= the grave/ sheol) and returned, so His statement is perfectly accurate. The grave itself (=sheol/hell) itself could not prevail against Him:
Jesus spoke Aramaic and called Peter ‘Kephas’, which means a huge rock or boulder.
Jesus did not speak in Aramaic. That is a large piece of scholarly nonsense. There is no Aramaic version of the gospels in existence, and it is their wilful ignorance and unwillingness to accept what we have right here bfore us which makes them talk such nonsense.
"So you are Simon the son of John? You shall be called Cephas" (which means Peter) (Jn 1:42)
That is point of the word play in Mt 16:18 “
And I tell you, you are Peter (Kephas), and on this rock (kephas) I will build my church,…”