Evaporation varies depending on certain factors, e.g. wind exposure, climate, time of the year (winter/Summer). With most pools, if your pool is losing more than 3- 5mm per day, you may have a leak.
Compare this with previous bills, if there is a noticeably larger difference in consumption, yes you may have a leak. Try the meter test; you may require leak detection services.
Yes, it is possible, when you have a crack in the suction line pipe, you tend to suck in air.
First check your pool cleaner is not clogged up with debris. If it is ok there is a possible leak in the suction line, which results in a lack of suction which in turn disables the cleaner.
If your salt water chlorinator is in working order, it should have no problem in keeping up the chlorine levels, if you are also adding salt and water on a regular basis, yes, it does sound like a possible leak.
It may be that your chlorinator is not producing chlorine.