1.
http://i.imgur.com/SiqNM.png that infographic should help (if its legible)
2. yeah, but I reccommend using XSE 1.1.1 (download here:
http://www.sendspace.com/file/qog56c)
3. you cant im afraid. to access the Tree pokémon data the special 0xAB needs to be activated from a script.
4. it should work the same as the infographic but you dont need to use the plugin part as it automatically loads the overworlds.
5. yeah, you need to index your sprites. there are tutorials on that in the tutorials subforum.
6. well, it depends on how often you want the rematches to be available and how. is it just using the vs seeker, or just after a certain event is done you can talk to them and rematch them again.
7. im not sure, sorry.