From a Biblical Unitarian perspective - those that hold scripture as being wholly sufficient to reveal all truth about God's salvation plan for man.
How do those who believe that Jesus is a created being understand the verses which say everything that was created was created by him?
Everything became through the Word, and without the Word did not become one that has become. John 1:3
This verse was quoted by OP as a proof that Jesus is not created. Does it say Jesus? No it does not - it speaks of the 'word' or 'logos' Gr.
When, we must ask did Jesus come into the biblical narrative? When the logos became flesh.
When was that? as John records in v14 (~4BC) Jesus is simply not mentioned anywhere until this point of his conception in Mary and subsequent birth. Equally, there is no 'Holy Son' mentioned either except in the form of a man who would fulfil various prophecies.
To persist with an imaginative and forced reading into the text is not necessary. If it says 'logos' it is not saying Jesus. Make no mistake, Jesus IS the logos, BUT only after it became flesh. We can see also very clearly that 1 John 1 expresses this logos as a 'which' - not as a person until manifested in Jesus.
From this simple reading of the text, we see that Jesus was not 'in the beginning', but the logos was. And with God, which also means not God.
Colossians 1:15-16 (NIV): The Son is the image of the invisible God, the firstborn over all creation. For in him all things were created: things in heaven and on earth, visible and invisible, whether thrones or powers or rulers or authorities; all things have been created through him and for him.
The context is once again vitally important here. Is Paul speaking of a Genesis creation as we read in John 1 and Gen 1? No he is not, he is speaking of the new creation, the church, the fact that all God's work in making man would be realised fully in and only in Christ. Without Christ - who is the image of God, we cannot be the image of God either. So all things are fully realised in this new age in Christ. (Rom 8:29) Same story for Romans 11:36 as OP quoted.
There is no validity in assuming from a traditional approach that Jesus was somehow born from all eternity. We need only note further the words of Col 1 carefully, "things in heaven and on earth". God created the earth and the heavens - not just the things ON the earth or IN the heavens. Again, this is not speaking of a Genesis creation.
The OP states, "I mean, that's pretty obvious." (That all was created through Jesus). Well, no it's not. Only if we read in that which is not there and make up stuff to fill any gaps we perceive from a faulty perspective. Jesus didn't create anything. He is the servant of the Creator, not the Creator. He received the spirit from God - making him again - not God.
“Here is My servant, whom I have chosen, My beloved, in whom My soul delights. I will put My spirit on him, and he will proclaim justice to the nations. Matt 12:18 (Luke 3:22)
To get around these obvious truths about Jesus not being God, a "two-natured" Jesus was proposed. That way he can be a man when he needs to be - like be tempted and die, to be flesh and not spirit, to be made heir and exalted to the heavens. And be a God when he needs to be to fit other dogma. This concept is not biblical but devised to distract from the biblical truth of the human Jesus, born of Mary with no pre-existence, made like us in every way Heb 2:17 If he is God also - he is not like us at all!
Extracts from; https://www.biblicalunitarian.com/ https://www.biblicalunitarian.com/verses