The source you cite here has 320 quotes, including multiple repeats. The author goes on to say "One word of caution: I am no expert in Greek". Warning noted. :)
I have posted several sources that show clearly this is not so, yet you never commented on them (which is fine with me), such as this one.
I don't know that I've passed on anything you've written directly to me. I may have passed on commenting on pings because I am like the author. :)
The most important thing is precisely Matt 1:23 because ALL Christian Bibles agree with the Septuagint against the Hebrew Bible. If we take exception from something, according to your own logic, it must not be inerrant.
I don't see it as an exception or a contradiction. The Hebrew allows for a virgin, a chaste young woman. When the prophecy was spoken it probably referred to who would become Isaiah's second wife. The virgin here is a type of the Virgin Mary.
What he does do very well is show that the Septuagint was the foundation on which the NT Scripture was built. There are only six verses where the Apostles quote Hebrew over Septuagint. In all other OT references (2/3), the Septuagint version is preferred, or both the Septuagint and MT agree (1/3 minus the six verse mentioned earlier).
I don't see it as an exception or a contradiction
But all Septuagint versions call her a virgin and not a young woman.