Mixed Content: The page at URL was loaded over HTTPS, but requested an insecure XMLHttpRequest endpoint URL. This request has been blocked; the content must be served over HTTPS

Here's your problem:

RewriteCond %{SERVER_PORT} ^443$
RewriteRule (.*) http://www.example.com/$1 
You don't allow SSL requests (443 port number is used for HTTPS requests). Try removing these lines.