How do deniers of Jesus preincarnate existence handle all the personal pronouns in John 1, particularly verse10?

Considering @OneGodtheFather's Answer given to the Question, I see that he had to expand his answer to 3 distinct answers, and in his latest comment he had to admit that "Yes, 1., 2., and 3. are different approaches to the text, and may not be compatible."

In my answer, the only thing that I will retain is the approach to the Greek text: the logos is referred to with the masculine pronoun (houtos, "this") for the simple reason that, in Greek, the word logos is of masculine gender.

So, it is a mere projection into the text that the logos-Word has a personal subsistence, distinct from that of God, the Father Almighty, before the Incarnation. In fact the interlude about John the Baptist at verses 6-8, has the literary function of preparing a “change of scene” between the pre-incarnated logos, and the incarnate logos.

So the fact that logos is a masculin noun does not mean at all that it is a "he", a person. Not before the Incarnation.

I believe that four main questions are outstanding, if one rejects the traditional-trinitarian approach:

1. What is the logos?
2. What does "in the beginning" (Grk. en archē) mean?
3. What does "the Word was with God" (Grk. ho logos ēn pros ton theon) mean?
4. What does "the Word became flesh" (Grk. ho logos sarx egeneto) mean?

Here are my answers to the 4 above (sub)questions.

1. The logos is, essentially, God Himself, it is the Greek rendering of the equivalent Hebrew word dabar, and, even more probably, of the Aramaic memra, a term used especially in the Targums (Aramaic translations-commentaries of the Torah) as a substitute for "the Lord", out of respect. There are good reasons to think that the Gospel of John, and in particular the Prologue, owes to an Aramaic text. If we want to introduce a distinct referent (not person) for the logos, it is appropriate to say that it is an essential attribute of God, just like His Spirit (Greek, pneuma; Heb ruach).
2. The Racovian catechism (quoted by GodtheFather at his no.2) affirms that "nothing else ought to be understood here besides the beginning of the Gospel". This is a projection into the text almost as artificial as the trinitarian claim that the logos is a "pre-existent", nay eternal "God-the-Son". The Greek expression en archē, translated in English "in the beginning" is the very same expression used in the Greek LXX version of Genesis 1:1 (from the Hebrew be-re'shiyth), and it is perfectly appropriate, because, both in Gen 1:1 and John 1:1, it is used absolutely. As for Mark 1:1, the authors of the Racovian catechism were using an improper example, with deliberate bias, because in that case the expression is not absolute, but explicitly the "beginning of the gospel of Jesus Christ".
3. The word pros is problematic, because it normally does not convey the idea of "with". There are other Greek prepositions, like meta, syn and para, that are normally used to express "with". The authoritative LSJ Greek English Lexicon, says that, pros + Accusative, in general, "expresses motion or direction towards an object", which does not seem to be very useful. At §III, though, it says that it expresses "Relation between two objects". This is quite close to my statement that "the logos is an essential attribute of God".
4. That same logos that was "closely associated" with God "in the beginning", by means of which everything was created, in the fullness of time "became flesh" (sarx egeneto) that is became essentially associated with the man Jesus. How? I suggest, at his virgin conception in the Virgin Mary. The virgin bith is the outer, miraculous aspect of the inner mystery of the Incarnation. Extending the notion of “conception christology” introduced by the late Catholic theologian Raymond E. Brown (An Introduction to New Testament Christology, 1994, pp. 144-5), I propose to refer to this understanding of the logos, of Jesus Christ and of their relatioship as Logos-Conception Christology.

As I said, my answer is against the traditional-trinitarian one, but also against the socinian-unitarian one (see OneGodtheFather's no.2).

It is obviously open for debate and objections.

1. Hold that the personal pronouns up to John 1:11 or 1:14 refer to the Logos but not Jesus.

In the particular line you are quoting, John 1:10, the pronouns can be understood to refer to the Logos. It can be translated as

"The Logos was in the world, and the world came into being through the Logos, and the world did not know the Logos."

Logos is a masculine noun, and so fits the pronouns here. If you think the Logos is not = to Jesus, then this line isn't stating Jesus pre-existed.

Indeed, this is basically how the Revised English Version translates this line, where they use 'it' instead of 'he' or 'him'. In commentary on John 1:10 they say

"John 1:10 shows that the logos, God’s express purpose and plan was in the world, and it also repeats in a different way what had been stated in John 1:3, that it was through the logos that God made the world. However, John 1:10 adds that the world did not know the logos and thus by implication the world did not know God."

It is possible to hold that the masculine pronouns are referring to the Logos right up to John 1:14's introduction of the 'only begotten'.

In the case of the Revised English Version commentary, they hold that John 1:1-10 is "a kind of inclusio," and then at John 1:11 John switches from the Logos to 'the Logos made flesh'.

2. Hold that the pronouns referred to above may or may not refer to Jesus, but also hold that the 'beginning' which is being talked about in John 1 isn't the beginning of Genesis, but the beginning of Jesus' ministry and the 'new creation'.

You see this with the Racovian catechism (p. 63).

"As then the matter of which John is treating is the Gospel, or the things transacted under the Gospel, nothing else ought to be understood here besides the beginning of the Gospel; a matter clearly known to the Christians whom he addressed, namely, the advent and preaching of John the Baptist, according to the testimony of all the evangelists, each of whom begins his history with the coming and preaching of the Baptist. Mark indeed (chap. i. 1,) expressly states that this was the beginning."

Compare John 15:27 ("you have been with Me from the beginning.") or John 16:4 ("from the beginning"). So what is being described at John 1:11 according to this is the new creation which has come into being.

3. Hold that John 1:1-5 refers to God's word, Jesus is referred to first at John 1:7, and is the referent straight through to John 1:18. This is the approach Anthony Buzzard takes in The One God, the Father, One Man Messiah Translation: New Testament with Commentary.

"1 In the beginning was the word, and the word was with God, and the word was fully expressive of God Himself. 2 This was with God in the beginning. 3 Everything came into existence through it, and without it nothing of what came into being existed. 4 In it there was life and that life was the light of men. 5 And the light shines in the darkness and the darkness does not overwhelm it.

6 There came on the scene of history a man sent from God. His name was John. 7 This man came as a witness so that he might bear witness to the Light and that everyone might believe through him. 8 He was not the Light himself, but he witnessed concerning the Light.

9 This was the genuine Light which enlightens every man coming into the world. 10 He was in the world and the world came into existence through him, and the world did not recognize him, the Light. 11 He came to his own land and his own people did not accept him. 12 As many, however, as did accept him, to these he gave the right to become children of God — namely the ones believing in his Gospel revelation. 13 These were born not from blood, nor from the desire of the flesh, nor from the desire of a male, but from God.

14 And the word came into existence, a human being, and tabernacled among us, and we beheld his glory, the glory such as a uniquely begotten Son enjoys from his Father, full of grace and truth. 15 John gave his witness concerning him and cried out with these words, "This was the one of whom I said, 'The one coming after me has now moved ahead of me, because he always was my superior.'" 16 For from his fullness all of us have received grace and more grace. 17 For the Law was given through Moses, but grace and truth came through Jesus Messiah. 18 No one has seen God at any time. A uniquely begotten Son, one who is in the bosom of the Father — he has explained God."

I have preserved the paragraph formatting from Buzzard's translation, as it helps highlight the flow of ideas.

Note the lower-case 'light' until John 1:7, which indicates the shift to a reference to Jesus (the logos made flesh). A key here is that the 'beginning' of John 1:1 on a straightforward reading refers to Genesis' beginning, but John 1:10 which seems largely a repetition is rather a development of John 1:3, applying the idea to the 'new beginning' which is the ministry of Jesus. So the 'world came into existence' at John 1:10 is referring to the new creation brought about through Jesus, not the original creation in Genesis.

Buzzard's translation is the first of John 1 (whether trinitarian or unitarian) I have read to make sense to me, as a whole and in terms of how it develops the narrative through John 1.