On line 270 you have to change the syntax slightly since it uses a text field and not the typical numeric ID field.
On line 270 update to:
onclick="document.getElementById('WADADeleteRecordID').value='<?php echo($row_WADAcaduser['UserName']); ?>';document.getElementById('deleteBox').style.display = 'block';document.getElementById('deleteMessage').style.display = 'table';" />
I just added quotes around the name value.