Some feedback:
1. huge cache size typically is due to page- or request-specific JS (or CSS) which you should either exclude (see FAQ), or you could tell AO not to aggregate internal JS (or CSS) (see autoptimize_helper.php_example)
2. the .php-files (instead of .css/.js) is because you configured AO to deliver the CSS/JS dynamically, but the same principle from (1) applies.
3. 410: check ;-)
frank