Your issue was that you were trying to run two AJAX requests at the same time, login and login_info. So, essentially, the Ajax.LastData returned was the data run by the last completed Ajax Request - the user's level - and the username was never returned back to the client side.
The easy fix was to run the login Ajax request and then when Ajax(login) is completed run the login_info Ajax request. The system gets one and sets the username then gets their level (admin or student) and sets that data to the user_Type variable.
Here is the corrected capx Here
All in all, you are definitely going in the right direction. You have done a very good job expanding upon the login system and even put my php skills to shame.
Imagine trying to code all of this in actionscript...
Thank goodness for C2.