This is how I understand it:
Jesus is the Son of God in the sense that He has the same nature of the Father, is sent by the Father as a submissive Son, and is loved by the Father as only a Father can love a son. First the nature part, when we are begotten by our fathers, we inherit their natures and qualities, i.e. our fathers are human therefore we are human. The same goes in the Son of God. Jesus is the only Son of God, or Unique Son of God in the sense that He has the same nature as the Father and the qualities of His Father. If Jesus has an identical nature of the Father, He would therefore be Deity as the Father is. Colossians 2:9 says that all the fullness of deity dwells in Him bodily. If Jesus is fully deity, then He would be eternal as the Father is, for a true God has no beginning.
The second point is that Jesus was sent by the Father in taking on the role of the Submissive Son. Jesus as the divine Son God is not literally born in time like a human son would be, but He has taken the role the Son in what is called the Economic Trinity, or better said, how the Persons of the Trinity interact with each other. The Father is the paternal hierarchy, while the Son is the Submissive Servant, who listens to the will of the Father in all things, and the Son would therefore be the inheritor of all things in being the Son of God. And the last point is that the Son is loved by the Father in a unique way that only a father can love of a son. This unique love is something that we will never experience with God, it is a love that has existed for eternity. And this Love proceeds from the Father and the Son as a Person and is whom we call the Holy Spirit, the eternal Love of the Father and the Son.
Now on the topic of the Word of God, this is best understood to me as the very utterance of the Father is the Son in action. He is the Messenger of God, the Revelation of God, the Creative Aspect of God, for God spoke the universe into existence, therefore Jesus was the very Creator of the universe being the Word that created all things. And God’s Word has always existed, for God has always had His Word, therefore Jesus being the Word is eternal.
And one last thought on the Jesus being the Word and the Unique Son of God, is that who better to reveal and explain the Father than His own Son, for Jesus said to St. Phillip, “He who has seen me has seen the Father.” Jesus is the very revelation of God the Father in being God’s own Word and God’s One of a Kind Son.
Hope that helps, God Bless!