1)
Why is it written Asher Mar'eh, and we pronounce it Ish Mar'eh?
1.
Radak: The writing means that he had an [awesome] appearance, and he was big. We pronounce it Ish Mar'eh, like the simple meaning (a big face).
2)
Why does it say here "Ish Mar'eh", and in Divrei ha'Yamim I, 11:23, it says "Ish Midah"?
1.
Radak: Also Ish Midah means big, like "Anshei Midos" (Bamidbar 13:32).
3)
Why does it say that he descended to him with a staff?