1)
Why does it mention the name of Hadad'ezer's head general?
1.
Rashi (Shmuel II, 10:16): It is because he was very strong.
2)
Here he is called Shofach, and in Shmuel II, 10:16 he is called Shovach!
1.
'Rashi' (from Midrash Tehilim on 3:2): He is called Shovach because he was (tall) like a Shovech (dovecote). He is called Shofach because he spilled blood ('Rashi' - like water).
2.
Sotah 42b: His name is Shovach. He is called Shofach because anyone who sees him is Nishpach (spilled) in front of him like a flask.
3.
Radak: Beis and Pei are pronounced from the same place (the lips, so they are interchangeable). We find "Bizer" (Tehilim 68:11) in place of Pizer. (Also refer to Shmuel I, 17:18:3:1.)
