Your arguments are thought provoking, Theocrat, and deserve some careful attention. My initial response, however, is that I don’t think you have proved the point you are trying to make, and you miss the thrust of the passage and the incident it is describing.

The context of the passage is, of course, parentage (of Jesus and the Pharisees), and the Pharisees have in mind the rumour that Jesus was an illegitimate half-breed (which they bring into the open in verse 48), and demon-possessed (in which sense, his ‘father’ is the devil). So the discussion revolves around this and their claim to parentage from Abraham (and Jesus’s accusation of their true ‘father’ being the devil, because of his knowledge of their disguised murderous intents). The focus on Abraham as the passage moves towards its climax arises out of these arguments. It is in this context that Jesus’s claims to relate to God as ‘Father’ acquire significance, as well as his own implied status and role as ‘son’ (verse 36). If the Pharisees rest their claim to status on an ancestry in Abraham, Jesus rests his on an ancestry in God.

Inexorably, the exchange with the Pharisees draws out the significance of Jesus’s identity. Instead of saying that God gives life to those who keep his (God’s) word, he makes himself the source of life and freedom from death, for those who keep his own (Jesus’s, not the Torah) word (v.51). In verse 52, the Pharisees draw the following conclusion: if Jesus is asserting that he can give life, then he (unlike Abraham and the prophets) will never die. Jesus then places Abraham in context, as one who ‘rejoiced at the thought of seeing my day’. The Pharisees assume that Jesus is claiming contemporaneity with Abraham, who had lived some 2000 years before, and that these are indeed the ramblings of a demon-possessed man. But Jesus does not allow them to remain in this delusion, and makes himself clear with the self-identification of verse 58.

The impact of his statement goes beyond saying that he was merely in existence before Abraham (before Abraham was, I was). It’s here that your attempted explanation falls considerably short. I will quote the whole statement:

“It only makes sense if Jesus is referring back to some statement he has made previously about his present status with respect to the patriarch. I would suggest that Jesus is expanding on his statement in verse 56 by explaining how, in spite of his not being 50 years old, Abraham could still have rejoiced to see his day.

Bringing the two together what we get is: “Before Abraham was, I am he… whose day Abraham rejoiced to see”.
This is a clear identification by Jesus of himself as the seed promised to Abraham by Yahweh and through whom all the families of the earth would be blessed.”

The explanation you provide is not clear at all, and does not make sense of the grammatical ‘confusion’ within Jesus’s language. If he only wanted to say that he was the promised seed whose day Abraham (would have) rejoiced to see (or rejoiced to see in a prophetic sense, or in a vision), he would not have said ‘Before Abraham was, I am.’ Jesus implies by saying ‘I am’ that he is the ‘always’ of YHWH. He doesn’t need to add anything - the Pharisees have understood and pick up the stones. He is saying something quite different from the ‘I am’ of the man healed of blindness in John 9:9. The context provides the difference. There is also a wider context - the six other ‘I am’ statements in John’s gospel, although this is the most explicit in terms of Jesus making a statement of relationship to God. (I would also add a context of the ‘I am’ statements in Isaiah 45, 46, 47 and 49, as well as the context of the statement in Exodus 3:14).

You draw attention to the use of the phrase ‘Son of God’, and of course there is a traditional level of meaning which does not imply a relationship of ‘Son’ to ‘God’ in a divine framework, still less a trinitarian framework. But the point is that John, like Paul, fills the phrase with added content - especially in his developed use of the Father/Son relationship, which is seen in John 8, as elsewhere in John. In the light of John’s gospel, the phrase has acquired far greater content than its previous usage. It is not a category mistake to see that it now has a significance filled out by Jesus’ use of the Father/Son relationship in which the term ‘Son’ has begun to acquire the significance of divine being within a divine relationship. It is in this light that we begin to see the use of the phrase in John’s gospel. (John even has Jesus’s accusers using the phrase this way in 19:7).

It’s not as if I am defending a case which has never been made before. This, and your own unitarian assertions, is a well-worn path, though I’m happy to tread it over again if you want to.