Since I am a theologian and not a historian, I might be able to contribute to the second part of your question. English is not my first language, so please be gentle.

The virginity of Mary is a concept that has had a huge impact on christian theology. Next to the question of roman societal language use it is important to understand that the biblical text that mainly puts forward that concept is the Gospel of Matthew, that was, with all due epistemic humility probably written 80/90 CE in a Syrian christian context of former jews. This question in itself is highly debated among academic theologians, but the majority opinion at the moment. The impact of roman language on this greek text of is a question in on itself, but if we approach the greek biblical text of Mt 1:23, it will only get more confusing:

ἰδοὺ ἡ παρθένος ἐν γαστρὶ ἕξει καὶ τέξεται υἱόν, καὶ καλέσουσιν τὸ ὄνομα αὐτοῦ Έμμανουήλ, ὁ ἐστιν μεθερμηνευόμενον μεθ΄ ἡμῶν ὁ Θεός. - Behold, the virgin shall conceive and bear a son, and they shall call his name Immanuel (which means, God with us).(ESV)

This is a quote from Isaiah 7:14, alas not directly from the original Hebrew version but the Septuagint (LXX) a greek translation of the Hebrew text. The septuagint is a judo-hellenistic translation into koine greek that, again with epistemic humility, connected the greek speaking jewish world with their religious texts; the majority of scripture was probably translated between 250 and 100 BCE in Alexandria.

So now that we have followed the path of this verse to its roots, it will become obvious why it is important. The operative word here is παρθένος, which is often translated as virgin. As is quite common with greek words, it's meaning is quite broad and actually can mean virgin, but also just young girl.^((Gemoll, Wilhelm, Karl Vretska, and Therese Aigner.) *^(Griechisch-deutsches Schul- und Handwörterbuch)*^(. MünchenDüsseldorfStuttgartWien: Oldenbourgöbvhpt-Verl.-Ges, 2006.))

So the question now is, what does the Hebrew text say in Isaiah 7:14?

לָ֠כֵן יִתֵּ֨ן אֲדֹנָ֥י ה֛וּא לָכֶ֖ם אֹ֑ות הִנֵּ֣ה הָעַלְמָ֗ה הָרָה֙ וְיֹלֶ֣דֶת בֵּ֔ן וְקָרָ֥את שְׁמֹ֖ו עִמָּ֥נוּ אֵֽל׃

The operative word here is הָעַלְמָ֗ה (Almah) which mostly signifies a young woman.^((Gesenius, Wilhelm, Rudolf Meyer, and Herbert Donner.) *^(Hebräisches und aramäisches Handwörterbuch über das Alte Testament)*^(. Berlin: Springer, 2013.).) You can check an English version of the Gesenius article here.

As is always the problem with historic and academic exegesis we now have a conundrum at our hands: Why did the LXX translation work with παρθένος which goes more in the direction of a virgin, whereas in Hebrew this would have probably been signified by another word: בְּתוּלָה? For some scholars it is only consequential to conclude that the translation in LXX ist simply wrong and they attribute the virginity of Mary to a translation error. Other scholars uphold the reading as a vrigin, if you continue the Gesenius article it gives several reasons for doing so.

It is important to note, that our probably earliest source, the Apostle Paul notes in Gal 4:4:

ὅτε δὲ ἦλθεν τὸ πλήρωμα τοῦ χρόνου, ἐξαπέστειλεν ὁ θεὸς τὸν υἱὸν αὐτοῦ, γενόμενον ἐκ γυναικός, γενόμενον ὑπὸ νόμον, -  But when the fullness of time had come, God sent forth his Son, born of woman, born under the law, (ESV)

This translation is correct, γυνή signifies a woman, the Apostle explicitly does not describe Mary as a virgin. While the notion that an older source automatically is closer to the truth is, in my opinion, correctly doubted in academia, it is quite noteworthy that the "virgin position" is a clear minority in scripture itself.

At the end of this short trip into academic biblical exegesis it is only prudent to talk briefly about hermeneutics. Depending on your position on the authority of the Bible and it's different books compares to each other, this question could be answered completely differently. How and why should and can the Bible constitute an authoritative source for your beliefs or the beliefs of the church? What role do the Coucils of the early church play in your belief system, that have codified a certain understanding of the doctrine of virginity? While an interesting and necessary task, the study of the Bible is often without clear and concise results.

In respecting the plurality of scripture and interpretation, which I hope I have given you a short insight into, it is simply not possible to get an evidentialistic conclusion on this matter that "settles it". One could say, it is a question of belief.