Don't change the class_path.php file.
As for the themes, please show me what your default theme for the entire site is by looking in your database under 'adopts_settings', that is, if you didn't change the adopts_ prefix to something else. I'd like to rule this out as a possibility, in case you changed 'main' to something else during installation.
Also, please post your config.php file contents so I can check for errors in the script path (hint: it should be completely empty unless your site is inside a folder inside it's directory). It should look like this (aside from the entries with '------' as those should be filled with relevant data):
define('DBHOST', 'localhost'); //DB Hostname
define('DBUSER', '------'); //DB Username
define('DBPASS', '------'); //DB Password
define('DBNAME', '------'); //Your database name
define('DOMAIN', '127.0.0.1'); //Your domain name (No http, www or . )
define('SCRIPTPATH', ''); //The folder you installed this script in
define('PREFIX', 'adopts_');