The Noam Elimelech (פרשת נא) explains this quandry like so: Light is one of the names we use to describe God, and (as a revellation of His essence) His Torah. Obviously God always existed and wasn't created, so the language of creation doesn't apply to light. However, God's light is pure and simple, it is unformed. When someone (generally a Tzaddik) learns Torah for the sake of God's name, according to the holiness with which he has purified himself, he brings down God's light in the learner's similarly purified form.
This in turn explains the phrase זכותו יגן עלינו - His [the Tzaddik's] merit will protect us. It isn't the Tzaddik's merit that protects us, but rather the purity (זכות) of his Torah learning, the purity of the form he gives to God's simple light that will protect us. [See the blog of the same name.]
He doesn't go into a discussion of why the term creation is used by darkness. It appears to my simple mind that perhaps it is obvious that darkness--that which hides Godliness--is a created entity. On the other hand, I've written otherwise in the past.