4.7.x behind reverse proxy

I am using an old 4.7.x installation behind a reverse proxy. The capacity of the connection between drupal and proxy ist the bottleneck of my current setup. The reverse proxy (apache 2.2 based) is located on a minimal vroot server, which is too small to run drupal itself (upgrading ist too expensive for me). The drupal site does neither use search engine friendly pages nor caching.

The reverse proxy works fine, but unfortunately i do not get it to cache the files locally in order to reduce the load on my slow line (standard DSL with dynamic IP address). Any ideas / help / suggestions / tutorials?

Thanks

Beate