1)
Why did He say "you will rule like all your heart's desire"? If he wants to rule over Yehudah, he will not fulfill this!
1.
Malbim: This was a requisite for kingship. Before he rules over the nation, he must rule over himself - over the powers of his Nefesh and desires, and make them submissive under the intellect. Then, you will be "Melech Al Yisrael."