hi, JakoThAn
try to add these lines above the $fields definition:
$commenter = wp_get_current_commenter();
$req = get_option( 'require_name_email' );
$aria_req = ( $req ? " aria-required='true'" : '' );
and then, the notice about the ‘Undefined variable’ of post_id, you could just leave the get_permalink() function with no parameters, which means throw the ‘post_id’ away!
hope this will help~