Addressing requested contradictions and the reality of biblical illiteracy
In his letter "Defending the Indefensible," Oren Piper said although it may be theoretically true that the Bible is the only source of Christian authority, this is not practically the case, and then asked me to respond to certain apparent contradictions in scripture.
Concerning the point, I agree with him. There are many Christians unwilling to take the Bible as their authority in practice because they are unwilling to give it the type of study it deserves. It is an error for Christians to take for granted the teaching of their pastors or traditions, and contradicts biblical examples (Acts 17:11). It is false that all congregations claim to be the only true church. You won't find that claim among Presbyterians, Baptists, Methodists or the Assemblies of God, for instance.
Concerning the apparent contradiction about seeing God: The confusion here comes from an incomplete citation of John 1:18. It is the one "who is at the Father's side" that has made him known, as the rest of the verse says. Jesus is that one, as John demonstrates in the rest of the chapter. That is why Jesus says only the one who is from God has seen the Father.
Another aspect of confusion comes from the way we think of vision. In terms of vision with the physical eye, no one has seen God, except Jesus. However, the biblical concept of vision is more expansive than ours and includes relationships. That Moses spoke face-to-face with God indicates that they were close friends, although literally seeing God's face would kill Moses.
Similarly, Jesus is saying in John 14:9 if his disciples know Him, they know the Father. A similar idea is behind Exodus 24:9-11; God represents himself with a vague image, and what the people see is the place where they meet God. Finally, concerning Genesis 32:30, scholars debate whether the man was God in human form or an angel. In previous stories of the patriarchs, angels represented God. However, Jacob says, "I have seen God face to face," resulting in the problem of a man who defeats God.
The most probable explanation is that the point of the text is not the identity of Jacob's opponent, rather that Jacob's name was changed and, with it, his identity. No longer would he be Jacob, the deceiver, but Israel, the one who struggled with God and was permanently changed by the struggle.