Sorry - sounds like you've been through it. If you're simply trying to export the data you can use phpmyadmin to export the contents of the MySQL database to a SQL file, or to a CSV where you could manipulate it with excel. Alternatively, you can run the php-7.x compatible version WHICH IS STILL IN TESTING https://github.com/RussH/OpenCATS/archi ... nTests.zip
This will install on PHP 7.0,7.1,7.2.. however there are some additional steps needed in PHP7.2 to enable mcrypt support (the short answer is to use PECL) if you wanted to carry on running OpenCATS.
The PHP 7.x version won't be tagged for release for a few weeks/months, as some of the unit tests fail.. that's more an issue of the unit tests not supporting php7 than an issue with the actual OpenCATS code.