1)
Why were there less from Yehudah than from other Shevatim?
1.
'Rashi': They did not need to declare David king. They already made him king in Chevron! (Malbim ? they came only for his honor.) The other Shevatim, who were with Bnei Sha'ul until now, needed to come to Chevron to declare David king.
2)
What is the meaning of "Chalutzei Tzava"?
1.
'Rashi' #1: They are those that are taken from the nation. This is like "Chalutzei Tzava" in Matos (Bamidbar 31:5).
2.
'Rashi' #2: It is zealous soldiers. This is like Retzei v'Hachalitzeinu.
