Maybe you should try doing a fresh install of wordpress on your local computer and simply import your website using the wordpress.xml file created via Tools > Export. If you do that, you can take a good look at the wp_options table as this may give you a clue as to what might be going wrong when you import the .sql file.
Chances are that your database query is not catching all the cases in wp_options (or the posts table for that matter – though you may not want to bother with the content, if you intend to reverse the process).
But first, find the link to style.css on the page that 404ed, as that may give you the clue you need.
Then go through wp_options, row by row if necessary, and last search the whole database to see what else needs catching.