1)
Why did he say that Hashem makes his feet like [those of] female gazelles?
1.
Rashi: A female's feet stand straighter than a male's.
2)
Did he run, or stand still?
1.
Radak: If I needed to flee, Hashem made my legs like those of gazelles, and my enemies did not catch me.
2.
Malbim: Even though Hashem gives to me the swiftness of a gazelle, I stand in my place and do not pursue anyone.