1)
What is the significance that the Sarisim came while he was still talking with them?
1.
Vilna Gaon: He could have broken the pole that he made. Hashem caused that the Sarisim arrived [before he broke it].
2.
Malbim citing Mahara: The Sarisim heard the dialogue, that Haman was saying that he still wants to persuade the king to hang him. Charbano was one of the Sarisim. This is how he knew that Haman made the pole 1 !