For the reference to the identifier in the validated field are you getting an error with it by default before you update it? I did a test and found that I had some fields referenced like this. In my testing the validations still seemed to be working just as they should. I'm not sure that this is a bug if it is not causing problems the way it is. Please explain a little more about this part and why you have updated it and what the difference is for you.
As for the session starting do you have the WAVT_ValidatedForm_PHP.php included at the top of your page? The first couple of lines of this file check to see if the session is started and if not it will start the session. Here is the code from the top of that page:
php:
if (!session_id()) {
session_start();
}
