What is the meaning of "l'Ru'ach Mishpat la'Yoshev Al ha'Mishpat"?
Refer to 28:5:3:1
Rashi: Hashem will give spirit to "Meshivei Milchamah" (Chachamim), to instruct rulings of Mishpat.
Radak: Hashem will give to Chizkiyah, who will be king and sit on the royal throne to do Mishpat, knowledge and understanding to rule correctly. It says "v'Nachah Alav Ru'ach Hashem Ru'ach Chachmah u'Vinah" (11:2). Chachmah and Binah are parts of the Ru'ach (Neshamah).
Malbim: A country needs two matters to succeed. (a) The king who wears the crown does Mishpat between people. The verse teaches that with "Ru'ach Hashem", he will do Mishpat. This is "la'Ateres Tzvi" (5). Also refer to 28:6:2:3.
Why does it say "veli'Gvurah"?
Refer to 28:5:3:1.
Radak: Hashem will be Gevurah for them. They will not need human strength against Machaneh Ashur. When they fought their enemies, and the war reached the gate of the [enemy's] fortified cities, Hashem defeated the enemy - "Hu Hikah Es Pelishtim Ad Azah
Why does it say "Meshivei Milchamah Sha'arah"?
Refer to 28:5:3:1