I write a lot of RewriteRule in my .htaccess
file , but problem occurs when I switch from https to http pages; it
I think this might be of your help
.htaccess redirect https to http not working
and for last question this might be of your help
http://httpd.apache.org/docs/current/rewrite/flags.html and
http://www.addedbytes.com/download/mod_rewrite-cheat-sheet-v2/png/
EDIT: You can try using
RewriteCond %{SERVER_PORT} ^443$
RewriteCond %{SERVER_PORT} !^443$
instead of
RewriteCond %{HTTPS} on [NC]
RewriteCond %{HTTPS} off [NC]
For detail
Please see this link, someone had similar problem. Please see second reply of the post
http://www.webmasterworld.com/apache/3228459.htm