Another Job Dilemma

The history:

This summer I took a job with a reputable and high paying private institute. I had friends who worked there, vouched for it, and it is a difficult job to get. The screening and interview process is rigorous and unlike most private institutes in Korea, they don't just hire anyone off the street. So when I started, I had some pretty high expectations about the professionalism, work environment and level of organization at my new school. But as it always seems to be, I was almost immediately disappointed when I discovered my supervisor what a nit-picky, inarticulate, paranoia-inducing jerk, and the school wasn't as organized as I had hoped it to be. Nor had they fulfilled all of their contract obligations to us (four people were hired at the same time) regarding our hiring, and while my co-workers weren't happy, they weren't willing to speak up for the things to which we were entitled. But I was designated bitch and lead the charge, and we eventually received everything we were supposed to get. Which lead me and said supervisor almost immediately into a vicious cycle of confrontation and passive aggressiveness that ended only when I was terminated, on the weekend via text message and email just 6 weeks or so after I had started.

I was shocked, pissed off, and thrown into immediate financial peril. Not to mention that I am here on a guest worker visa, which is terminated when your job is terminated... Oh, the problems were really starting.

So when the owner of this institute offered to extend my visa, somewhat indefinitely, if I would substitute a class here and there, I couldn't really refuse. I need money. And even more than that, I need a visa. So this little agreement has lead to apologies, followed by more steady work, and now followed by a full-fledged job offer at a new school that she just opened, where I happened to substitute for her yesterday. Where the money is good, and where I'll be teaching little kids again, and where the hours are somewhat normal (now I teach at night, which is convenient for the time-being, but I'd like a normal 9-5...)

Is refusing this job a case of too much pride? I know I've been apologized to, but the way I was fired was just so dirty. I feel so burned. And I feel like they know they made a mistake in firing me and not that damn supervisor (actually, after I was fired, then talked to, then apologized to, they investigated a little more and discovered the inarticulate prick was the problem and not me, and he got the boot, too)... I don't want to refuse what might be a good job, but I also don't want to put myself in the path of getting burned again. Because it has become all too clear to me that this boss is not afraid to burn people. Now I am in the unique position of doing "favors" for her by subbing. I say when; I dictate the rate of pay. I am a free agent. But if I'm contracted to work for her again, won't that relationship change?

Oh, the headache... What should I do?