Out of curiosity...

If you want to create a Plugin (by using the Plugin API), there is no need to unpack and repack the game. You just have to download the latest PluginAPI.jar (which can be found here) and add it to your IDE - then you can start making plugins. To load a plugin, you have to compile it and move the resulting .jar file into the "plugins" folder in the game directory. That's it.

Here you find information about the basic requirements: Getting started

This topic contains some information about how to create a plugin: Create a Plugin

This is the documentation which contains all classes, methods and events (some of them also include example code): https://javadoc.rising-world.net/

This section of the forum contains a few example plugins (with the according source code): https://forum.rising-world.net/board/31

Yes that's basically possible with the current API^^

I don't know if they have fixed this yet but, be careful of the size of explosion you are setting. We would have demo parties on my server, when I ran a server, and when we set off to many sticks of TNT at the same time the server would crash.