I don't know where you got the idea that Gentile Christians "use Christ as the only God". It certainly wasn't from any church that teaches the Bible properly, and it certainly wasn't from any Bible school that is faithful to its text.
I don't believe that the Bible teaches that "Christ is part of God". Nor do I believe that the OT God is exclusively the Father, though I understand why some might think so. John 1 tells us "All things came into being through Him, and apart from Him nothing came into being that has come into being. In Him was life...." That means that Jesus is the Creator!
I encourage you to review your beliefs in light of the early heresies. Your view, as described above, is dangerously close to subordinationism.