Can't access 2nd site dashboard

Hi,

I recently modified a live WP 3.5x install so that it supported a network of sites. So far so good. I can see the menu item in the top left. The core WP installation is in a sub-directory off the root folder called "/portal".

The problem I'm having is when I'm trying to access my 2nd site's dashboard.

When I created the 2nd site, the Add New Site page showed the following form fields:

1. Site Address (example.com/) then the blank field below it. - Which I entered "/portal/site2".
2. Site Title: "Site2"
3. Admin Email. ...

After pressing the "Add Site" button, the new site appeared in the list of Sites, but when I navigated to Visit Site from the "My Sites" > "Site2" > "Visit Site" I was taken to a Page Not Found page that uses the stylesheet from the /portal website.

This is what my Network Setup suggested I place in the wp-config.php file in /portal:

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'www.gbotechnology.com');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

This is what my Network Setup suggested I place in the root .htaccess file:

RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).*) portal/$2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(.*\.php)$ portal/$2 [L]
RewriteRule . index.php [L]

Questions:

Is it possible to add a second site to a sub-directory install?

What should the value for item 1 be in the Add New Site page form?

Because it's a sub-directory installation, should there be an .htaccess file in the root directory as well as /portal?

What should the /portal .htaccess and wp-config.php files say in them?

Thanks!