What is "Ben Dodo"?
Rashi, Targum Yonasan: This is his name.
Why does it say here "Ban Achochi", and in Divrei ha'Yamim I, 11:12, "ha'Achochi"?
Radak: Achochi was the family name. Therefore, it says here Ben Achochi. There it says ha'Achochi, like Ben Kenaz [is called] "ha'Kenizi" (Bamidbar 32:12).
Did David have only three Giborim?
Rashi: These were the strongest.
Radak: Elazar was the third in this war, and he was the head of this war.
What is the meaning of "b'Charfam ba'Pelishtim"?
Rashi: They shook hands and agreed to fight against them and defeat them.
Radak: This is like "Cheref Nafsho Lamus" (Shoftim 5:18; he risked his life).
Targum Yonasan: B'Chasidu Pelishta'ei. (They reviled; Yonason translates also "Cherfuni" and "Cherfu" (Yeshayah 65:5, Tzefanyah 2:10) as Chasidu - PF.) Radak- he explains that the prefix Beis in ba'Pelishtim is extra.
Malbim (9,10): This is the episode below (verse 13) with the field of lentils. It is clear from Divrei ha'Yamim I, 11:13 that this was in Pas Damim.