registration and login with e-mail pass

As you have discovered, what you want to do is not configurable through the WP admin. However, you can definitely do this with WordPress, either by adding some custom code to your site, or an easier way would be to install a plugin (or two). As an example, I found this one to handle the email address as username: http://wordpress.org/plugins/wp-email-login/ There’s also a free version of WP User Meta http://wordpress.org/plugins/user-meta/ which might be able to handle these requirements

I’ve never tried either of these so I can’t vouch for them. Plugins offer an easy way to extend the standard functionality.

If you want to try this on your own, this page is a great place to start:

http://codex.wordpress.org/Customizing_the_Login_Form

It does require some technical knowledge though – and I need to warn you in advance about editing the functions.php file. It’s very easy to bring your site down completely with one tiny error. Make sure you take a backup of the file before you make any changes, and have your FTP login instructions at the ready, so you can access the server to restore the backup if anything goes wrong.