Apache mod_deflate not compressing javascript and css files

The first issue is that you have the element with a directory from the file system...

This is from the Apache manual:

When to use <Location>. Use <Location> to apply directives to content that lives outside the filesystem. For content that lives in the filesystem, use <Directory> and <Files>. An exception is <Location />, which is an easy way to apply a configuration to the entire server.

When I setup mod_deflate on Apache I use this setup:

# --------------------------------------------------------
# Deflate Module Configuration
# --------------------------------------------------------
<IfModule deflate_module>
  # Set the location to webservers root
  <Location />
    # Insert the filters
    SetOutputFilter DEFLATE

    # Netscape 4.x has some problems
    BrowserMatch ^Mozilla/4 gzip-only-text/html
    # Netscape 4.06-4.08 have some more problems
    BrowserMatch ^Mozilla/4.0[678] no-gzip
    # MSIE masquerades as Netscape, but it is fine
    BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

    # Make sure proxies don't deliver the wrong content
    Header append Vary User-Agent env=!dont-vary

    # Make sure to never zip binaries (ie6 and chrome has issues with this.)
    SetEnvIfNoCase Request_URI \.(?:gif|jpe?g|png)$ no-gzip dont-vary
    SetEnvIfNoCase Request_URI \.(?:exe|t?gz|zip|bz2|sit|rar)$ no-gzip dont-vary
    SetEnvIfNoCase Request_URI \.pdf$ no-gzip dont-vary
  </Location>

    # Enable mod_deflate logging by uncommenting these lines
    #DeflateFilterNote Input instream
    #DeflateFilterNote Output outstream
    #DeflateFilterNote Ratio ratio

    #LogFormat '"%r" %{outstream}n/%{instream}n (%{ratio}n%%)' deflate
    #CustomLog logs/deflate_log deflate 
</IfModule>

Probably the ProxyPass / directive you have in your config routes all requests to the Tomcat backend, bypassing all your mod_rewrite directives. You can try to remove the ProxyPass directive and use RewriteRule with the [P] flag after your other rewrites:

• mod_rewrite: P|proxy

For the expire headers the situation is worse — in another similar question a solution was not found.

Option +FollowSymLinks would be needed for using mod_rewrite in .htaccess files; in your case it is not required, because you can put everything in the Apache config. Moving rules from config to .htaccess is pointless and can only make things slower. However, there is an important difference between .htaccess and the Apache config — in .htaccess patterns in RewriteRule are matched against relative filesystem paths (which never start with /), while in the VirtualHost context these patterns are matched against the URL path after the hostname, which always starts with /. Therefore at least one of your rules is incorrect:

RewriteRule ^content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

should be

RewriteRule ^/content/(js|css)/([a-z]+)-([0-9]+)\.(js|css)$ /content/$1/$2.$4

(note the additional slash in the beginning).