They're offering me 30 pln per 45 minute lesson Net for, at the minimum, 20 hours a week.
Not that bad IF they are paying for your accommodation IN FULL (rent, building maintenance fees, utilities).
Forget about it if you have to cover these costs yourself. You won't break even for the year if you take your airfare and visa fees into account, even if you only stay until the end of the academic year (early or mid June).
Remember, you are only going to get paid for 30 weeks out of the year. That's a measly 6000 bucks a year. 500 bucks a month, or 1500 PLN a month. A little more if you stay only until June. Minus your airfare and visa, of course. You MIGHT earn a little during the summer, but don't count on it. Also, don't count on getting any private students to supplement your income during your first year.
Even if you manage to convince them to pay 45 zl per hour, that doesn't change the fact that you will not break even if you have to pay for your accommodation, and barely break even, if at all, if you do not have to pay for accommodation.
You will not be able to learn enough Polish to communicate easily in nine months or a year. Unless you are planning to stay for many years, it's best to forget about learning Polish beyond a few basic phrases. It's a devilishly complicated language that takes a lot of grammar knowledge to express even simple things. It isn't a "plug-and-play" language like English.
The only reason to come would be as an extended vacation, part of which you will be able to earn for, part of which has to come from your own savings. In any case, this is not a viable stepping stone to career advancement. There are much better options to enhance your resume elsewhere.
As for racism, you will have people stare, but more out of curiosity than hostility. You might hear occasional unwelcome comments from drunken low-lifes, which it is best that you ignore. Violence in Poland is rare, unless alcohol is involved, so don't drink and steer clear of intoxicated individuals. Your students might have some bizarre ideas and ask silly or inappropriate questions, again more out of curiosity and unfamiliarity than out of hostility. If you are assertive, self-assured, open, friendly, self-confident and understanding of ignorant, but otherwise innocent and good-hearted, people, you'll be fine. If not, forget about it.
Small town life has its advantages. It's cheaper, in general, and you will be able to develop closer relationships with people. That is, if they decide that you belong.The disadvantages are that there is little to do for mental stimulation. You will find yourself going to Katowice or Kraków just to get out. I myself spent my first four years in Poland in a small town with 50,000 people. Some of the people I met there are still among my closest friends ten years after.