Both China and Korea clients uses same AES Encryption for lobby and game. The difference between China and Korea is only in auth stuff. As I mention already Korea uses SRP6 encryption algo with custom RC4 key generator, you can find those algos here in "building BNS emu from scratch". It will work for any KR version.
Login server port is 6600 now. You must be using really old one CBT client. Actually, you can edit config files by using shared util named "DATED", I think you can still download it here. It won't work with the latest one KR client because they changed AES/XOR key. If you know how to use Hex editing stuff, I can help you with new key.
Themida unpacking is needed, at least when you are working at very early development stage.