1)
Why does it say "Avshai"? In the rest of the Sefer he is called Avishai!
1.
'Rashi' (Divrei ha'Yamim I, 19:11): In all of Divrei ha'Yamim he is written and pronounced Avshai; these are the only two exceptions 1 , based on Mesorah. The Sefer is for David's honor; it should not sound like David's sister's son is important like himself, that also his Av is Yishai. In the rest of Sefer Shmuel he is called Avishai; Yishai was his grandfather.
1
I did not find these exceptions in our text. 'Rashi' does not specify what is the other exception. There is no other mention of Avshai there between Perek 3 and Perek 17! (PF)