I am currently building a site and this is definitely an experience that I can learn from. I am wondering, why was the homepage not being cached?
"Note that in 0.8.44 behaviour was changed to something considered more natural. As of 0.8.44 nginx no longer caches responses with Set-Cookie header and doesn't strip this header with cache turned on (unless you instruct it to do so with proxy_hide_header and proxy_ignore_headers). "