John 3:16 clearly has two persons: 1. God, who sends, 2. His Son, who is sent. Whether his Son is God himself, the Bible does not make clear, because we are not supposed to know. But I think if the Son is God, he would be another person, not the Father, who is the one who sends him.
1 Tim. 3:16 has textual variants. There is evidence that some scribe misunderstood the Greek word hos 'who' as abbreviation of Theos 'God', so he wrote Theos. Therefore I think the textual variants with hos are older, and with Theos, are in error. The Bible is careful not to tell us if Jesus is God or not. So verse 16 does not have God.
At the end you are asking us if 2 Cor. 5:19 is true. My answer is yes, it is true. Note that the verse distinguishes between 2 persons, God and Christ. So I disagree with Oneness Pentecostals that the Father is Christ. There are two persons here, one God the Father, and the other Christ, who might be another person of the Godhead, we cannot know. We just cannot know everything about Christ, see Luke 10:22. And likewise we cannot know everything about God, how many persons he is, one, two, three or more than three.