1) Air pollution is bad enough, but it depends on which part of city you will stay. However, it doesn't show as it's highly polluted, according to worldwide index of air quality ()
2) Eating out in not expensive in contrast to major world cities. Roughly medium level lunch is 10$, but you can still find luxurious/cheaper places.
3) It may vary depending on international/national/private types. Regular school year year starts Sept 1, finishes May 25. There are three interim breaks in Fall (beginning of November), Winter (end of December), Spring (end of March). The major school holiday is throughout all summer.
4) Yes, it has, Almaty is the most developed city in country. However, there are not many English speaking activities.