The best way at this moment is to download source code as I did. Source Code of jBPM and related Drools elements. and than read it:) Problem is that as far as I can see it call all change very rapidly.
1)Sry, I also haven't found it yet...
2) We are trying to do the same. We've found that it would the easiest using the gwt-console-server with rest: http://localhost:8080/gwt-console-server/rs/server/resources.
3) No idea.