My wordpress multisite is not working again, and I suspect htaccess problems

I run a small one-person nonprofit with WP Multisite. I finally got it working but it is painfully slow, so following Bluehost recommendations, I installed the supercache plugin and that broke everything. I think we got rid of that, and Bluehost tech support guy was able to restore the main site by sticking in the htaccess code from HIS WP multisite. So now it's time for me to fire up some of our extra sites--we do events, and we have websites for all of them. But when I tried to open our Mardi Gras site, it wouldn't open--too many re-directs.

So I futzed around and now discover that: a) I can't properly create a new site (it shows up in the network dashboard, but not in the "My Sites" dropdown; b) All my subsites have lost their themes. Main website is http://www.clarendon.org. One example of a broken website would be:http://clarendon.org/clarendonday2013/

Here are my current htaccess and wp-config files:

Current htaccess is this:

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

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^(wp-(content|admin|includes).*) $1 [L]
RewriteRule ^(.*.php)$ wp/$1 [L]
RewriteRule . index.php [L]

Current wp-config.php is this:

define('MULTISITE', true);
define('SUBDOMAIN_INSTALL', false);
define('DOMAIN_CURRENT_SITE', 'clarendon.org');
define('PATH_CURRENT_SITE', '/');
define('SITE_ID_CURRENT_SITE', 1);
define('BLOG_ID_CURRENT_SITE', 1);

For some reason, the Bluehost folks saved an htaccess file from last May--and I think things were working in May....

htaccess May 27:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index.php$ - [L]

# add a trailing slash to /wp-admin
RewriteRule ^wp-admin$ wp-admin/ [R=301,L]

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

</IfModule>

# END WordPress

Any ideas about how to resurrect my sites?