Jesus is not claiming to be God here: "On him God the Father has placed His seal of approval.” How much clearer can this be? He is clearly showing that he and God are distinct individuals. In order for someone to place their “seal of approval” on someone else there must be two distinct individuals. For one individual to approve another individual, there must be one person who approves, and another person who is approved.
It is not as if Jesus is God and God needs to create a fake approval process to boost Himself. God does not need anyone's seal of approval. But Jesus is clearly illustrating that he has been empowered by God to deliver God’s message to these people.
And the "oneness" that Jesus once indicated between himself and God is their unity of purpose: Jesus does God's will, so there is a oneness of purpose. God has given Jesus His “seal of approval” because Jesus is carrying out God's will.
Being saved is not an automatic process by which we simply say "I surrender to Jesus" and then we are saved. It is not as if Jesus' "dying" on the cross automatically saves anyone. We must apply Jesus' teachings. It is Jesus' teachings that saves us. And what was his primary teaching?
“ ‘Love the Lord your God with all your heart and with all your soul and with all your mind.' This is the first and greatest commandment.” (Matt. 22:37-38)