Looks like you are not passing your file to the closure:
Mail::later(20,'emails.formFollowup', array('status'=>$status, 'JobNumber'=>$apmformdata->JobNumber), function($message) use ($file_to_save) {
$message->to('name@domain.com', 'My Name')
->subject('APM Form Alert Notice')
->attach(use ($file_to_save));
});