1)
Melech Ashur sent Seforim to Chizkiyah (verse 14); the curses were written on them (Divrei ha'Yamim II, 32:17). Why did he need to make Sheluchim to say all this?
1.
Malbim: The Sheluchim said concisely what was in the Seforim.
2)
Above (36:7), he said that Hashem will not save Chizkiyah because he removed the Bamos. Why did he not say so now?
1.
Malbim: Now he addresses Chizkiyah, who knows that he did like the Torah commanded!