Few things (looking at your dropbox file):
1. You probably want global $post; before if ( $post->post_type == 'sp-event' ).
2. I see your add_filter hook (single-event.php) but there’s no the_content();. Also it might be better to put your hooks in functions.php.
3. Try to start from scratch, as simple as possible. Add code back in piece by piece, and see where it goes wrong.
Good luck!
