1)
Why did he say that he should wear the royal garments
1.
Vilna Gaon: This is the only matter that [Haman] lacks.
2)
Here, Haman mentioned the crown. Why did he not mention it in verse 9, and why didn't the king give it?
1.
Rashi (9): Haman saw that the king was upset with the idea of putting his crown on another person, so he omitted this 1 .
2.
Vilna Gaon, Malbim #2: He meant 'the Levush and the horse that the king rode on the day 2 that the crown was put on his head.'
3.
Malbim #1: Some say that they put a crown on the horse's head.