1)
What is the meaning of "Niv'ashu"?
1.
Radak: It is detested, just like a person hates something spoiled.
2)
Here it says 20,000 foot soldiers from Aram Tzovah and 12,000 men from Ish Tov (excluding Melech Ma'achah's men). In Divrei ha'Yamim I, 19:7, it says 32,000 chariots!
1.
Malbim: We must say that the number of foot soldiers was the same the number of chariots. Here it mentions the foot soldiers, and there, the chariots.