1)
Why does it say "I insulted the Jewish camp today"?
1.
Malbim (9): Initially he did not insult them; he merely told them to pick someone to fight according to the custom (refer to 17:9:1:1 and the note there). When he saw that they did not agree, then he insulted them.
2.
Malbim: Even if you do not agree to settle our claim based on a fight between two men, send a man to fight me like normal war! Now that I revile and blaspheme you, you must pick someone to fight me to defend the honor of your nation! This is why David fought him.
