I give you my opinion and tried to explain you how this is working. Maybe i’m wrong, maybe not. And my english is not the best  for explaining such subtilities.

Perhaps others like @hnla or @mercime will give you better advice.

you asked for any clean solution for my members to register without using a username.

Registering is a WP process who need a username and a email. Those 2 information are provided by the user at his first visit when he decide to subscribe to your site, OK ?

Now you wonder how FB or Google can connect without username ? They use it !…[Read more]

de nada ! 😉

Fortunately there has plugins ! It’s your choice.

for css styling, be inspired by this: http://www.php-ease.com/code/wordpress-style-admin-bar.html

If you want to code something into the Toolbar, you have to play with the wp_admin_bar […]