1)
Why did he begin "you, the king"?
1.
Ibn Ezra: King - hear this!
2.
Malbim: The introduction was to inform him that he is king due to his father. Hashem gave kingship to Nebuchadnetzar, and via this, to his sons - "v'Avdu Oso v'Es Bno v'Es Ben Bno."
2)
Why did he say "Malchusa u'Revusa vi'Ykara v'Hadra"?
1.
Malbim: Malchusa is becoming king initially. Afterwards Revusa (it increased) - he conquered Malchus Ashur. Afterwards he received Yekar and Hadra (honor).
