You are making the point that the description of Jesus as Son in the Nicene Creed as “proceeding from the Father,” is somewhat speculative. I agree that it is. However, it may be helpful to look at where this idea came from historically. The historical problem is that in the fourth through sixth centuries there were many attempts by Christians to come up with a precise definition of the nature of God and, more specifically of Christ and the relationship between the Father and the Son. The problem arose because those who sought to present a “logical” picture (something that Greek Christians wanted very badly because of their obsession over philosophical questions) often came up with a clearly unbiblical picture. There was Arius who concluded that Jesus was created and is not God. There was Sabellius, the father of Sabellianism or Modalism, who said that the Father, the Son and the Holy Spirit are not persons, but different “modes” of one person–God. There were other false theologies. The mainstream of the Church wanted to allow the precise relationship between the Father and the Son to remain a mystery, which is exactly where the question ought to have remained. But, in view of the false theologies–and perhaps even heretical theologies, the early church fathers were virtually forced to come up with some sort of more precise definition.
Out of this came the idea that the Son eternally “proceeds” from the Father. They based this definition on passages such as John 6:57 and John 1:18. I will agree with you that this is theological speculation. And you are right that, if this is a correct description of the relationship between Father and Son, then the Father is “causally prior to” the Son. This does not imply temporally prior, but causally. Then, of course, the Eastern and the Western church fought over the silly distinction (silly in my opinion) of whether the Holy Spirit proceeds from the Father only or from the Father and the Son–the point of division for the Great Schism.
My response, is that this idea that the Son “proceeds” from the Father is not in direct contradiction with Scripture. In fact, there is some wording in the Book of John which be used to support this idea. But, it is not a slam dunk, and the exact meaning of the passages in mind leave some significant room for interpretation. It is speculative theology at best. But we are not like the early church fathers who were, in effect, trapped into producing a clear and definite statement that I believe they did not want to make. We can leave the exact, precise nature of the relationship between Father and Son as the Bible leaves it–a mystery!!!
What I suggest we do is simply state what the Bible also clearly states. Jesus is God. Jesus is God, but he is also called Son of God. This seemingly illogical relationship is where the word Trinity comes from. We do not need to embrace the words trinity or proceeds, but we need to recognize that Jesus is God. He is not created. He has been with the Father from the beginning of time and even “before” there was time. Jesus does submit to the Father, so there is some sort of subordinate role that we do not need to fully understand or define. That Son is co-equal with Father and at the same time submits to the Father is clearly established by Scripture, so we can leave it there. We do not need to say that the Son “proceeds” from the Father. As you point out, this definition is somewhat speculative. Neither do we need to criticize those who use this terminology. All we need to do is explain why we hesitate to use this terminology, love those who do, and ask them to love those who do not.
You make one statement that I am not sure I agree with. You say (paraphrasing) that “Every single person must possess wholeness and every aspect of it–that every person must be self-existing.” To this I reply: Who says? Who makes this rule? Do human logical rules apply to God? Like I said, when human beings try to apply logical human assumptions to God they tend to get into trouble. We need to leave some questions to mystery and let what God said speak for itself. I will agree that what you say seems “logical,” but then again, John said of Jesus, “In the beginning was the Word. The Word was with God and the Word was God.” This clearly breaks some humanly logical rules, so we need to let the mystery remain. We ought to be careful against pridefully forcing what seems logical to us lower beings to one who is clearly way above us.
Last thing. We need to remain humble and allow people to have different thoughts on this. Some distinctions are not a matter of salvation. Those who deny deity to Christ (Arians, Jehovah Witnesses, etc.) may be outside of Christ, but most of these other theological speculations are not a matter of life and death.
That is my feedback.