1)
Why did he say "Chalilah Li Hashem"?
1.
Radak: This is like me'Hashem. Also "Elchanan ben Dodo Beis Lechem" (verse 24) is like mi'Beis Lechem.
2)
Why did he say "ha'Dam ha'Anashim"?
1.
Rashi: This is said in astonishment. Metzudas David - would I drink their blood?! Radak (16) - since they risked their lives, the water is considered like their blood.