About whether Isaiah 7:14 says virgin or young woman... You interpret scripture with scripture. If 2 scriptures seem to conflict, then you'd better look closer because you're wrong about 1 or the other.
Compare IS 7:14 with Luke 1:34-35. The angel has just told Mary that she'll have a baby. Mary says how can this be because I'm a virgin. Some versions say she doesn't have a man. Either way, it's plain that Mary knows where babies come from and she knows she hasn't done what's necessary.
Matthew 1:18 names the father - the Holy Spirit. "This is how the birth of Jesus Christ came about: His mother Mary was pledged to be married to Joseph, but before they came together, she was found to be with child through the Holy Spirit."
Matthew 1:20-23 also calls her a virgin and again names the father, the Holy Spirit. Mary hasn't been unfaithful. 20 But after he had considered this, an angel of the Lord appeared to him in a dream and said, "Joseph son of David, do not be afraid to take Mary home as your wife, because what is conceived in her is from the Holy Spirit. 21 She will give birth to a son, and you are to give him the name Jesus, because he will save his people from their sins." 22 All this took place to fulfil what the Lord had said through the prophet: 23 "The virgin will be with child and will give birth to a son, and they will call him Immanuel"— which means, "God with us."
As far as the NT not calling him Immanuel, Immanuel is Hebrew. The NT is written mostly in Greek with some parts in Aramaic which was the common spoken language in Israel at the time. Immanuel in Hebrew means God with Us. Jesus, in Greek, means God is Salvation, or some variant of that. The names Immanuel and Jesus are essentially the same, just in different languages.
“In a time of deceit telling the truth is a revolutionary act.” ― George Orwell
It's not over when you lose. It's over when you quit.
