So, OK, I will chime in (again); I'm probably less versed in this stuff than Dsarker, but I might know a thing or two. I'm not native English speaker, which makes some explanations harder for me, but I will try my best nevertheless, again.
I will start editing this post to answer as much stuff as possible soon.
Just keep in mind, my dear atheists, that whatever argument you have found, somebody probably have found it before, and it was answered by smarter people than me (like, St. Thomas, for example); so even if I can't find an answer, that doesn't mean there isn't one, and just because you think you have original idea, doesn't really mean that you have.
@GavJ - regarding changing doctrine and dogmas:
The short answer is: not everything that Pope says is doctrine. Not to mention dogma. And even they can be wrong about stuff. This is especially relevant to the first quote you present, getting only one counter-example to what is stated in modern catechism, even if it was spoken by the Pope.
As for the second set of quotes:
Quote of Pope Pius XII is completely irrelevant to the canon 847, as it explicitly talks about people who have
separated themselves from the structure of the Body; this means that they have heard the Gospel and chosen not to be part of the church; Bible quote is intentionally misinterpreted by you, as the full verses say:
8 He will punish those who do not know God and do not obey the gospel of our Lord Jesus. 9 They will be punished with everlasting destruction and shut out from the presence of the Lord and from the glory of his might
and it is clear from the second part of the 8th verse that "do not know God" means here "
actively do not know God", as in act as there is not God (and thus disobey the Gospel). In multiple places in this chapter it is noted that faithful will be rewarded, and later in the same letter it is spoken about the deceivers, and that Thessalonians should know the truth. Nothing there suggest that God is going to actively punish people who have not heard of Him; this is reinforced by the fact that Thessaloniki are in Greece, one of the places where it was easiest and fastest to spread the word of God and most people there should have heard of it, but might not have chosen to follow it.
The rest of the quotes there seems to have similar purpose, and be more about heretics, than people who never heard the Gospel; those were all spoken at times when most, if not all people in the world were considered to either know the word of God (in Europe), be heathens, nevertheless knowing the word of God (Middle East/Africa) or be non-existent (no Americas for you, and barely any knowledge of Asia; the parts of Asia that were known then also have, in general, heard about Christianity).
Also, the quotes from single people, still. Those can not be considered doctrine just because you found them, you know? The doctrine is written down and passed down the generations, and becomes important part of the Church Tradition (capital T).
I will try to continue later, but time is scarce now.