1)
How was Barzilai great?
1.
Rashi: He was very wealthy.
2)
What is the meaning of "bi'Shivaso"?
1.
Radak: It is like bi'Yshivaso. The first letter of the root is omitted, just like it is omitted from the Makor (infinitive) "b'Shivto" (Mishlei 31:23).