"Basically what I'm asking is what happens if you find out that your employer is a scumbag and you want out? What are your options then?"

Reply: If you find out after you took a job that your Korean employer is a scumbag, then the scumbag is you for not talking to other esl teachers working at the school before you took the job and make sure that the school was good.

Anyway, I suggest you China, they only check criminal backgrounds and no previous schools problems as I know. Japan and Korea share info about teachers if requested, mostly the ones deported.

I really hope that you realize that you are in somebody else country before you call locals scumbags. Bad start.

Good luck.
PS: no offense to you with my english grammar, english is just my second language.