Hi
Free
Well that's a fairly sweeping statement that if we don't understand exactly how Jesus' relationship with his Father works, we've got the wrong God. Got any evidence that any of that is true?
The deity of Jesus isn't a matter of not "understanding exactly how Jesus' relationship with his Father works," but of not understanding the nature of Christ as the Bible reveals him. He is the central figure of Scripture, to whom the law points, in whose name alone we have salvation, who created all things and in whom all things are held together, and to whom every knee in creation will one day bow. It stands to reason, then, that we cannot just believe he is whoever or whatever we want him to be, but that we must believe he is who he said he is.
John 1:12 says that "to all who did receive him, who believed in his name, he gave the right to become children of God" (ESV). To "believe in [on] his name," is to believe in "the sum of the qualities which mark the nature or character of [Jesus] . . . to accept as the the revelation contained in [Jesus Christ the Son of God]" (M. R. Vincent, Word Studies in the NT). Jesus repeats this in John 3:18. This is also what is meant by "name" in Matt 28:19, the sum total of the divine being--the Father, the Son, and the Holy Spirit.
Mormons believe Jesus is the literal spirit child of the Father and his celestial wife. JWs believe that Jesus was the archangel Michael who came to earth and then returned to being Michael. Others believe Jesus is only human. But all those things cannot be true (and none of them are), yet each thinks they have the true Christ. Again, it stands to reason that we cannot have such conflicting notions and still believe that all who believe those things will be saved, even though all will say they believe Jesus is the Son of God.
2Co 11:3 But I am afraid that as the serpent deceived Eve by his cunning, your thoughts will be led astray from a sincere and pure devotion to Christ.
2Co 11:4 For
if someone comes and proclaims another Jesus than the one we proclaimed, or if you receive a different spirit from the one you received, or if you accept a different gospel from the one you accepted, you put up with it readily enough. (ESV)
Notice that Paul is pointing out errors and that one can actually believe in a different Jesus.
Also, to either accept or not accept that Jesus is God is also a denial of the nature of God as revealed in Scripture. Would you agree that this is included in Jesus's words that we are to "worship God in spirit and in truth"? If our conception of God is not true, can we really worship him in truth? What God would we then be worshipping if it isn't the God of the Bible?
We also see in Romans 10:9-13 that Paul equates "calling on the name of Yahweh" with confessing "Jesus is Lord." So, it very much seems to me that who we believe Jesus to be is affects our salvation.