Please use http://adobe-consulting-services.github.io/acs-aem-commons/features/versioned-clientlibs.html . This was implemented to handle this issue. This issue is not related to AEM per se. IT is just the way css is cached by the browser.
selvaganesh..Edition publishing separation pattern is a standard pattern for this use case. Please have a look at this article by Martin Fowler. http://www.martinfowler.com/bliki/EditingPublishingSeparation.html
You can cache the webservice responses either in AEM or use a reverse proxy like varnish for this. You can set ttls like every few hours clear the cache and refetch..You can run these services in author once and push to publish as nodes. This depends on the type of data.
LDAP can be configured to sync users on login. Since you wanted to add users before, you need either syncallusers or syncexternalusers (you need to send used ids as json like["<dn>"]