who is the "son of man"/"son of god"?

If the Greco-Romans, misunderstood the text because they transliterated a verb into a name, then why does Jesus call himself "son of man"/"son of God"?  Doesn't that mean he is saying he is semi-Divine?

No.

"Son of man" בן אדם in Hebrew, is a phrase used in Numbers 23:19, in the Psalms, in Isaiah, in Jeremiah and throughout Ezekiel.  It means, essentially, "human."  In Greek, the phrase is υιος ανθροπου.  It still means "human." 

"Son of God" is a phrase that occurs once in TaNaKh: it appears in the book of Daniel, after Shadrach, Meshach and Abednego have been thrown into the furnace (Dan 3:25): "He answered and said, I see four men loose, walking in the midst of the fire, and they are not hurt, and the form of the fourth is like the son of God."  

Daniel was  one of the youths delivered to Nebuchadnezzar for the purpose of being trained to become a Babylonian. Daniel resisted.  The narrative of Daniel includes Daniel interpreting Nebuchadnezzar's dream--a revisiting of the Joseph narrative. Joseph, was, of course, a son of Jacob.

The fact that the gospeller uses the phrase from Daniel creates another link between gospel text and the phrase in Numbers, referring to the "star out of Jacob."  The fact that the Daniel narrative concerns a foreign king attempting to oppress Judeans, and a Judean resisting oppression adds to the internal evidence that suggests the gospel text was produced at the time of the bar Cochba revolt (when the newly reinstituted Land of Israel was threatened, and ringed by the fire of Romans who wanted its destruction).