What is "Kol Gevuraso"?
Radak: In his wars and against the Kushim (Divrei ha'Yamim II, 14:8-14).
What is the meaning of "Chalah Es Raglav"?
Radak: He became ill from his feet. Also "Hem Yatz'u Es ha'Ir" (Bereishis 44:4) is like Min ha'Ir, and similar verses.
In Divrei ha'Yamim II, 16:12 it says "b'Raglav Ad l'Ma'alah Chalyo." 'Rashi' there says that swelling in his feet extended all the way to his skull. Malbim says, to higher parts of the body.
Why did he get sick?
Radak citing Sotah 10a: One who uses Chachamim [for his work] is not cleansed [without punishment. He used Chachamim to build these cities.]
Gra (Divrei ha'Yamim II, 16:12): Because "va'Yratzetz Es ha'Am" (16:10), i.e. [he broke] their feet, he was punished Midah k'Neged Midah.
