Hi @michaelsync and welcome to the community 
i think there is a little missunderstanding in your calculation 
let me try to explain:
Elasticsearch is bundled with SonarQube for the Community-, Developer-, and Emterprise Edition. On the Datacenter-Edition you can separate these components.
With this knowledge we can look again at your calculations and the origins of those:
these are the requirements come from using elasticsearch with another product and do not reflect the usage of sonarqube with elasticsearch. as we bundle it anyways you can scrape these requirements from your calculation.
increase the Disk Space here. The database can easily take more than 512 MB of storage. it depends on the amount of code and analysis that are made by your team on how much space is required here. I would go for 8 GB to start with and monitor if this is too big/small.
hope that helps on narrowing down the requirements you listed. in any case you should monitor if your initial size can handle the load as each team works differently with SonarQube, which might change the hardware requirements.