1)
Why does it say "Hoy Achi v'Hoy Achos"?
1.
Radak #1: This is eulogy of relatives. They say Hoy Achi for a man, and Hoy Achos for a woman.
2.
Radak #2: Perhaps v'Hoy Achos refer to Yehoyakim's wife, even though she was not mentioned.
3.
Malbim: Yehoyakim's brothers and sisters will not be eulogized.
2)
What is the meaning of "[Hoy Adon] v'Hoy Hodo"?
1.
Rashi: Woe to his glory.
2.
Radak, Targum Yonasan: This is eulogy of a king. Hodo is his power and beauty, i.e. kingship. The Hei at the end is in place of a Vov, like "Ohalo" (Bereishis 9:21) and similar verses.