1)
Whose days should be few?
1.
Radak: The head of David's haters.
2.
Malbim: Their curse is that David's days be few.
2)
What is "Pekudaso"?
1.
Rashi: His grandeur. This is like "v'Yafked ha'Melech Pekidim" (Esther 2:3).
2.
Radak: The matter over which he is appointed, i.e. his money or wife.
3.
Malbim: His appointment - he was an officer in the army [should be given to another in his lifetime].