1) Yes - Tools > Database Diff
http://www.oracle.com/technetwork/issue-archive/2012/12-sep/o52sqldev-1735911.html This Oracle Magazine article takes you through the steps. We've updated the technology to make comparing schemas where you don't have login privs to the target schema easier in the latest and greatest version of SQL Developer. You can read about those updates here http://www.thatjeffsmith.com/archive/2012/09/using-database-diff-to-compare-schemas-when-you-dont-have-the-destination-user-password/
2) Where are you looking at the count? Are you looking at the grid toolbar space where it says 'All rows fetched: X in Y seconds' or are you doing a physical row count in the grid? We don't have enough information in your question to properly answer it. What are you seeing vs what are you expecting to see?
Edited by: Jeff Smith SQLDev PM on Jan 3, 2013 8:45 AM