How to send an email that always contains all fields of entityform, without manually updating when fields are changed?
This is already handled in the Entityforms Notifications sub-module the way you are describing.  

There is a view mode called "Email".  That view mode controls which fields show up in the email. This is done via a token in Rules.

In Entityform 1.x this token is controlled via the Entityform module itself.  In Entityform 2.x this is controlled via the Entity to Text Module.

I think there is some problem in Entityform 1.x with showing fields with multiple values. But this should work in Entity To Text.  You could also just use Entity To Text with Entityform 1.x.  Just replace Entityform 1.x token with the Entity To Text token in the Rule.

If you are interested this handbook page should probably updated with this information: https://drupal.org/node/1679794