1)
Why did David's men rely on the second answer? They did not rely on the first answer (verse 3)!
1.
Malbim (4): Refer to 23:3:2:1. This time, Hashem said "Ani Nosen" - miraculously; "Es
1
Pelishtim" - the entire nation.
2
1
In verse 3, Malbim distinguished between Makeh Es and Makeh b'. Perhaps he similarly distinguishes between Nosen Es and Nosen b'. (PF)
2
Surely, he means all the Pelishtim who came to Ke'ilah. We find that Pelishtim attacked shortly after this (verse 27)! (PF)
2)
Were their flocks in the war?!
1.
Radak: David struck them severely and chased them to Eretz Pelishtim, and took their flocks.