[Buggman]

Doesn't this "Virgin" Mary stem from a mistranslation of ancient Hebrew texts...where the texts prophecied the Savior being born to a 'young woman' which got mistranslated into 'young virgin'?

Nope.

Why does Christianity need the Savior's mother to be perpetually virgin?

It doesn't. It needs Miryam to be a virgin at the time of Yeshua's birth for three reasons:

1) To fulfill the prophecy of Isa. 7:14
2) To confirm the truth of the accounts of Yeshua's birth as given by Matthew and Luke, and
3) To sidestep the blood-curse placed on the line of Jeconiah (cf. Jer. 22:30)

But there's no reason why Mary would have to remain a virgin after His birth, and the fact that she did not is indicated by Mat. 1:24-25: "And Joseph, being roused from sleep, did as the angel of the Lord commanded him and took his wife, and did not know her until she bore her son, the First-born. And he called His name Yeshua ('Salvation')."

[Blzbba]

Thanks for the 'Nope' link!!

Another question: How was it proven that Mary was, indeed, a virgin at the time Jesus was born? Seriously, wouldn't Joseph be the only one who could confirm that? Or is this another 'leap of faith'? Again, just asking. Based on your previous response, I'm sure you'll point me in the right direction!