Without headless a lot of (for a server) unneeded dependencies needs be installed (on Debian stretch), like icon sets and x11-utils. Elasticsearch works without problems when you only install openjdk-8-jre-headless (that has much less dependencies).
Consolidated all basic configuration steps for the ideal case to top of document, moved all memory-related and "advanced" configuration to bottom. Removed remote Elasticsearch config from document entirely and replaced it with a link to ES documentation on the topic instead.
Jeroen