Oops, I forgot to respond to your question about Mark being a disciple of Peter. Most bibles introduce this gospel by mentioning this commonly accepted view, but I also found the following by doing a quick Internet Search.Abogado del Diablo said:How do you know that any of those were written by apostles? How do you know that Mark was written by a disciple of Peter?
http://www.bible.org/page.asp?page_id=1692An Introduction To The Gospel Of Mark
By: David Malick
I. AUTHOR: JOHN MARK A. Strictly speaking, the Gospel is anonymous B. EXTERNAL EVIDENCE strongly supports John Mark as the author of the Gospel of Mark in association with the Apostle Peter1 1. Pseudo-Barnabas ([5:9; Mark 2:17] c. A.D. 70-130) 2. Polycarp (c. 110-150) 3. Hermas (c. 115-140) 4. Papias (the bishop of Hierapolis A.D. 140) wrote in his last work (Exegesis of the Lord's Oracles) the strongest evidence for Marcan authorship tied to Peter:2The Elder said this also: Mark, who became Peter's interpreter, wrote accurately, though not in order, all that he remembered of the things said or done by the Lord. For he had neither heard the Lord nor been one of his followers, but afterwards, as I said, he had followed Peter, who used to compose his discourses with a view to the needs of his hearers, but not as though he were drawing up a connected account of the Lord's sayings. So Mark made no mistake in thus recording some things just as he remembered them. For he was careful of this one thing, to omit none of the things he had heard and to make no untrue statements therein.3 For more go tohttp://www.bible.org/page.asp?page_id=1692