1)
Why did David send to Ish Boshes? He already sent to Avner!
1.
Radak: This was for Ish Boshes' honor. He did not want to take her without Ish Boshes' permission (refer to 3:13:2:1).
2)
Why did he mention the 100 foreskins of Plishtim?
1.
Radak and Malbim, both based on Sanhedrin 19b: Sha'ul said that my Kidushin was valid, for I intended for Kidushin via the loan (Sha'ul promised wealth to the one who will kill Galyus). Really, I intended to be Mekadesh through the foreskins, and not via the loan (Sha'ul promised wealth to the one who will kill Galyus). Even though David gave 200, he said 100, for the stipulation was only for 100. .
