A gold pocket watch that John Jacob Astor IV was wearing on board the Titanic when the ship sank in 1912 sold at auction Wednesday in Chicago for $800,000. Freeman’s, the West Loop auction house handling the sale, had predicted the timepiece would fetch between $300,000 and $500,000. The watch buyer is an Irish businessman, according to Freeman's.A gold pencil case also recovered from Astor’s body went for $160,000, after fierce bidding that sta…