1) I't does not use Grafana. Try adding 60*
to the beginning of the Value-field:
Example: 60*((datasources["Factorio"]["ProductionStatsCurrent"]["coal"]["Produced"]-datasources["Factorio"]["ProductionStatsPrevious"]["coal"]["Produced"])/datasources["Factorio"]["SecondsBetweenTicks"]).toFixed(2);
2) The statistics can be found here: datasources["Factorio"]["Players"] so you should be able to create a listing on the "Dashboad" using the HTML-widget. It is not currently possible to show on the "Leaderboard".
3) No Discord yet. Here or on the email listed on the website.
4) Sorry, no triggers. But a great idéa, I'll add it to my todo-list.