The Power Messenger admin pages use Themes from Framework Builder. You could create a framework builder theme from your css sculptor design to apply that design to the admin.
Just make sure the template you create from the css sculptor design has the same editable regions.
The admin login relies on a session variable AdminLogin having the same value as the admin login you set during the install.
in your regular admin login page, edit the authenticate user server behavior, on the third step, click the lightning and select the password column to store it in a session. Name the session AdminLogin