Book of Esther Manipulation

There's plenty of manipulation afoot in Esther. In a negative way, Haman manipulates the king into approving genocide (though, that sort of stretches the definition of manipulation since he essentially just asks the king point-blank if he can do it). And in a positive way, Esther manipulates the king and gets him to throw two banquets, which she uses to convince him to end the plot to kill Mordecai. So, there's a little manipulation here, a little there—and it all comes out well in the end.

Questions About Manipulation

1. To what extent does Haman manipulate King Ahasuerus, and to what extent is Ahasuerus just a bad guy who jumps on the opportunity for genocide like it's nothing?
2. Conversely, to what extent does Esther manipulate the king? Is she pretty sincere in her dealings overall?
3. Why doesn't Esther request King Ahasuerus to kill Haman at the first banquet? What's the point of waiting through two banquets?
4. Is King Ahasuerus unusually easy to manipulate? What does this say about his character?