The word God is used in two different ways in Scripture. Firstly, the word “God” is used to refer to the Supreme Being of the universe who is the ultimate source of all things. Every time the Bible refers to the one true God it is referring to this supreme being who is the one that was before all else and from whom all life ultimately came. In this sense no one else is God. But the word God is also used to refer to someone who possesses the attributes of divinity, or the characteristics of God.
Many times the Bible teaches that Jesus Christ is the begotten Son of the one true God the Father, and being the Son, He possesses the same attributes and characteristics as His Father. It is an obvious fact that every son inherits the nature of his father. And since Christ came out of the Father, He is of the very substance of His Father and hence has the same God nature of His Father as He possesses by birth all the attributes and characteristics of His Father. In fact Hebrews 1:3 says He is the “express image of His person.” A son also and always rightfully takes the name of the father and so Christ as the only begotten Son of God has rightfully the same name. Note that Hebrews 1:1-9 says that Jesus is an heir who has by inheritance obtained a more excellent name than the angels and that name is God! So Jesus inherited His Father’s name, character and divine nature in the same way a human son inherits the human nature and name of his parents.
So Jesus is God because He is the Son of God. But He is not and cannot be “God the Father.” He is the “Son of God” just as the Bible so plainly states more than one hundred times. He is God's literal Son. To say that Jesus is God the Father is to say that the “Son is the Father” which means the Son is not really a Son and the Father is not really a Father. Or to put it another way, to say that Jesus is the Father because He has the same God nature as His Father is no different to saying that since my Father is Human and I am Human, therefore I must be my father! This is not good logic or theology and suddenly hundreds of Scriptures supposedly would no longer mean what they say at all. The truth is that Scripture means what it says and says what it means. God is the Father of Christ; Christ is the Son of God.
Satan's plan is for us to deny the Father and Son as this is what John called antichrist. 1 John 2:22-23. He does not care if our belief is Trinitarian, Unitarian or other. As long as it denies Jesus is the literal Son of God which also denies God is a Father. Confessing Jesus is the Son of God is our only means to the Father and to deny this has eternal consequences.
In conclusion, Jesus is not “a” God or “the” God but God only by nature through inheritance being the Son. Jesus is a divine being but He is not the supreme being. The Father is the supreme being and the source of all things and the life of the Father flows through the Son and out to all. Jesus is the channel through which all things come and why the Father has given all things into His hands. Only the Father is described as the one “of whom are all things.” He is the great Source of all. Jesus is not another source “of whom are all things.” That would make Him another God. Rather Jesus is described as the one “by whom are all things.” The Father has given Christ authority to rule over all things but this does not include the Father Himself. The Father is greater in authority and always will be. God the Father is the source of all things including His Son. Thus all things proceed from the Father; including Christ Himself, but it has pleased the Father that in Him should all fullness dwell (Colossians 1:19). So when we say “Jesus is God,” we have to be careful to state exactly what we mean. Christ is a divine being, but not the supreme being. When we speak of the Supreme Being there is only one such person and it is not Jesus.
“But to us there is but one God, the Father, of whom are all things, and we in him; and one Lord Jesus Christ, by whom are all things, and we by him.” 1 Corinthians 8:6
“One God and Father of all, who is above all, and through all, and in you all.” Ephesians 4:6
“The man Christ Jesus was not the Lord God Almighty,” — (E.G. White, Ms140, September 27, 1903)
“He [Christ] was not the Father but in him dwelt all the fullness of the Godhead bodily,” — (E.G. White, Lt8a, July 7, 1890)
“God is the Father of Christ; Christ is the Son of God. To Christ has been given an exalted position. He has been made equal with the Father. All the counsels of God are opened to His Son.” — (E.G. White, 8T 268.3)
“Only one being in the universe besides the Father bears the name of God, and that is His Son, Jesus Christ.” — (J.E. White, Coming King, p. 33)