You could start by testing on a local server: How to set up a local server using xampp
. Usually 500 errors are due to malformed .htaccess files. Try setting up a test server and then adding the sections to the .htaccess one section at a time. You probably have a typo somewhere; the .htaccess default error message is intentionally vague to avoid giving information to hackers (the Apache logs may contain more info; try searching Google for hints).