1)
Why does it say "v'Achiv Eliezer"?
1.
Malbim: The Sefer wants to teach that Shelumis was the fifth generation from Eliezer, [Gershom's] brother.
2)
What is the meaning of "Rechavyah Vno vi'Yshayah Vno"?
1.
Redak: Rechavyah was Ben Yeshayah. Rechavyah was Eliezer's only son, like it says above (23:17). Yeshayah, Yoram, Zichri and Shelumis were Bnei Rechavyah; he had many sons (ibid.) Shelumis was the head of them - "Shelumis v'Echav Al Kol Otzeros ha'Kodoshim" (the coming verse).
