Three Questions Three questions were asked, and the second one will be dealt with first. In particular, who is the 'Son of Man'?
Intertestament Judaism had several books that are extant today, which dealt with Messianic expectations, as well as other topics. One of these, 2 Esdras 13:3,
"sees something like the figure of a man come up out of the heart of the sea...this man flew with the clouds of heaven" (v.3)He defeats the hostile cosmic powers and delivers captives through a series of actions which precede the confirmation of his reign. (J.J. Scott, Jr., Backgrounds, p.311)
Some see a similarity between this and Daniel 7. Another Jewish book, 1 Enoch depicts the Son of Man at length, in the section on "Similitudes and Parables."
Some examples are:
The Son of Man was given a name, in the Presence of the Lord of the Spirits, the Before-Time [Head of days], even before the creation...He will become a staff for the righteous ones...He is a light of the gentiles, and will become a hope of those who are sick in their hearts. (48:2ff)
The righteous and elect ones shall be saved on that day...The Lord of the spirits will abide over them; they shall eat and rest and rise with that Son of Man forever and ever. (62:13-14)
J.J. Scott summarized the Enoch rendition of the Son of Man: "It is evident that the Enochic Son of Man is preexistent, heavenly, and majestic, He possesses dominion and will judge all humankind and angels." (Backgrounds, p. 313.)
But not all Jews shared the same concepts. Ancient Judaism, like the multitude of modern Protestant denominations, was diverse in its interpretations and teachings. Rabbinical schools differed, as well as sects, and apocalyptic cultists at the time of Christ.
Other Jews So what did other Jews believe about the Son of Man? There was a Jewish carpenter (mason) from Nazareth who shared some of the beliefs of the cultural writings, AND He had the audacity to apply them to Himself. He self-described Himself over 80 times as "the Son of Man"! This was Jesus. And it was recorded that this title was synonymous with "Messiah" and "Son of God." (John 5:22-27, 12:34)
The Jewish rabbis, scribes, and rulers of that time preferred a militaristic Messiah to free them from the Roman occupation of their land, and strongly opposed Jesus' use of "Son of Man." They considered it "blasphemy" (Mark 14:61-64, Mt. 26:63-65). [Although Pontius Pilate detected "envy as the reason for opposition.]
Today, there seem to be traces of dealing with the title of "Son of Man" as a synecdoche: a collective representation of Israel as a whole. Instead of recognizing a personality, they consider Israel as a whole to be represented. The treatment of the "Suffering Servant of Isaiah 53 is treated this way too. [Check with your local synagogue, for confirmation; see J.J. Scott, p.315]
Third Question Why the differential of this Person from the Ancient of Days? All throughout the ministry of Jesus, there was an expression of His reliance upon "the Father." He only did what He saw the Father do. He was to ask the Father to give the Church the Holy Spirit. He submitted to the cross because of the will of the Father. (John 15:26, chapter 17)
So it is appropriate that Jesus (Son of Man) is pictured as having to approach "The Ancient of Days" in order to receive His kingdom. This is recognized as a title of God (the Father). As far as the Incarnation goes, subservience examples are okay...without demeaning Jesus's triune deity.
First Question Is it still understood to be Messianic (according to Jewish interpretations)? It must be kept in mind that, while it may be considered Messianic, there are a multitude of ideas about what kind of Messiah is described! Pre-Christian era...First century Church era...Middle ages...modern times...they all have different Jewish expectations of Messiah (Son of Man).
So while many, or even most, consider this passage to be Messianic, it wouldn't be the Christian Messiah they anticipate. Jewry, as a whole, still rejects Jesus to be the Son of Man. (Orthodox, Reformed, Conservative; but see "Jews for Jesus" for many who do believe.)