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Customized HTTP to HTTPS redirect with drupal multisite

I have a multisite setup with drupal 7.23 which is working fine. Websites are like this:

SITE1

http://www.site1.info

SITE2 and 2 subdomains

https://www.site2.com
https://sub1.site2.com
https://sub2.site2.com

SITE3

https://www.site3.com

As you can see site2 and site3 are full SSL anabled but for site1 I have only some pages with SSL like this:

NO SSL:

http://www.site1.info
http://www.site1.info/page1

SSL:

https://www.site1.info/page2
https://www.site1.info/page2/subpage1

I have enabled non www. to www. redirect which drupal is offering by default and adjusted it a bit:

RewriteEngine on

  # I've also added these 2 lines to redirect HTTP to HTTPS because the next 3 lines didn't worked.
  RewriteCond %{HTTPS} !=on
  RewriteRule ^ https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

  RewriteRule ^ - [E=protossl]
  RewriteCond %{HTTPS} on
  RewriteRule ^ - [E=protossl:s]

  RewriteCond %{HTTP_HOST} .
  RewriteCond %{HTTP_HOST} !^(www|sub1|sub2)\. [NC]
  RewriteRule ^ http%{ENV:protossl}://www.%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

BUT here is where I'm stuck: if I access for instance: https://www.site1.info it s not redirected to http://www.site1.info and keep SSL ony for the desired pages. I'm not sure how to write all these rewrite rules given the fact that I'm no htaccess expert.