1. check items folder in IGCData and check drop folder and you just basicly need to start learning every config files related to what you want to change, and change it and experiment in game.
2. not sure there might be config for store but havent seen it yet in my experience.
3. cash shop editor for muemu season 9 google it, find it, there are plenty of people asked the same, just need a research and then u can use that editor and edit your cash shop.
4. play with the settings.. if it says 3% make it 3 and see in game if its 97% usually this shouldnt happen on files like IGCN... i feel like there is something wrong with ur configs.
5. check gameserver.exe for errors or whatever logs why it does that exactly when it moves u and figure out, i dont really believe this repack is good for you of season 9.. maybe try a different one like these
https://mega.nz/folder/etUwSIyb#z3E_XbTo0iPOexNPD20Zcw
6. put FO set on u and full stats, i mean u can ofc, there different ways.
7. balance it!!!!!!!! find calcchar.xml file in character folder in Igcdata somewhere and play with the setings, skills of bk damage, defense etc...
same applys to other characters, u need to test all this 1 by 1 alone with ur friends and spend time.
cheers