Now, what is worrying me is that I have come to understand that having a true or perfect understanding of God, is not only unnecessary but also impossible. For me, I've felt like the important aspect of faith is growth is understanding. So, how does this relate to the Creed?
Or, is this creed considered a deviation from the Orthodox faith emphasizing mystery?
We cannot fully comprehend God, but there are things we can know about him because he has revealed them to us. But that revelation, as we have received it, is not always self-evident. For example, both Orthodox and Arians cited Scripture to support their beliefs.
Leaving aside this particular Creed, the point of any Creed is to summarise our faith and what we can say about it or how we can express it, and in doing so it delineates the limits or the boundaries within which we understand properly.