1)
Why did Shlomo command to kill Yo'av only now?
1.
Radak (28): David had told Shlomo him to wait for a [new] misdeed to kill Yo'av for it. When he heard that Yo'av grabbed onto the corners of the Mizbe'ach, he said, this is somewhat of a rebellion - he thinks that he can be saved from me, and he remains in his rebellion, for I did not command to kill him. Therefore, he told Benayahu to strike him 1 .
1
This is unlike Sanhedrin 48b. It says that Shlomo accepted on himself David's curses against Yo'av (for Shlomo would execute Yo'av for killing Avner, and it is improper that Yo'av be cursed and executed for one Aveirah). (PF)
