1)
Why is he called a Na'ar?
1.
Rashi: This was before [he appointed him].
2)
What is "l'Chol Sevel Beis Yosef"?
1.
Rashi citing Targum Yonasan: He collected the taxes from all of Yosef, i.e. Menasheh and Efrayim, for he was from Efrayim.