This is particularly true when the mind, leaving the ground of experience beneath itself, rises toward the regions of the absolute Being, where, according to the strict requirement of natural theology, every metaphysical concept must be re-evaluated with the triple method of God-knowledge.
Again, you're quoting essentially verbatim the ideas of Plato and Plotinus. Plotinus especially very practically inferred the concept of striving to 'rise' to the upper echelons of reality, and to finally become unified with the One
The general rule of speaking about the Trinity is: everything in God is one, where there is no contrast of relations; therefore, if the excellence of nature is the predicate, the subject can be nature or a person; if the predicate is personal excellence, the subject can only be a person.
It is true, that if all things come from one being, God, it follows that all the things that come from it carry its essence and substance. This is why Plotinus could say that we should strive to unify our 'inner divinity' with the divinity of the One, since it only became separated by means of the limitations of the human mind, which you also explain and quote from the philosopher above.
Describing his relelationship with God using the terms "Father" and "Son" is of course a perceptive analogy, but this does not prove that the Son was created or that he is ontologically inferior to the Father, just as it is not in the human world.
At best, we can say that both interpretations (Trinity and non Trinity) are technically correct. Trinity because all things come from God and carry his essence. Non-Trinity because Jesus himself said "the Father is greater than I"..his very own words. And they cannot simply be discarded as words for the less enlightened or ignorant. Even if you did, we can say Jesus was saying the same thing in two different ways.