No, Almah was never used to be Virgin. It did not say that it was not virgin, but never referred to sexual purity at all. . It means 'a young girl/woman of marriageable age'.
And, no, God did not inspire the NT authors at all. NO more than God inspired Joseph Smith or Mohammed.
As for 'how blind the Pharisees were.. well, all that means is that the writers of the N.T. were angry at the Pharisees , because they were kicked out from worshiping with them, since their belief system had become heretical
Almah never referred to 'only a virgin'. In the Song of Solomon, almah is used in a very distinctly sexual situation, where it is most definitely NOT a virgin.
I really like how these fundamentalist Christians think they know Hebrew and the Jewish faith better than Jews.