1)
What is "Kol Cheshek Shlomo"?
1.
Radak, from Divrei ha'Yamim II, 7:11: Everything that he put to his heart to do in Beis Hashem and in his house, he succeeded.
2.
Malbim: Beis Hashem and Beis ha'Melech were necessary. Additionally, he built buildings without need, just due to desire to do many things, like he wrote "Higdalti Ma'asai Banisi Li Batim" (Koheles 2:4).
