1)
To whom does "Eleh" apply?
1.
Redak: The three mentioned - Heiman, Asaf and Eisan. They were Roshei Avos of the Leviyim. For their honor, their lineage is traced [at least] until Levi.
2)
Why does it say "u'Vneihem"?
1.
Malbim: It means with their sons.
