Humidity should be low. You do not want any excess moisture especially in the winter. It is the excess moisture plus the freezing temps that cause frostbite. It sounds like you are doing it right.
If you are not getting frost/condensate and have no objectionable odor, chances are very good that your humidity is fine and if it were me I'd just call it good.
But if you want to actually put a hygrometer out there and get numbers -- first, you need to check whether your hygrometer is ACCURATE, as a very high proportion of them are NOT, use Search to find the salt method for calibrating hygrometers, well ok it's not true calibration but you know what I mean -- then generally anything in the 40-80% range is pretty good, especially more towards the middle of that range. You do not want humidities over 85%ish if it can be avoided (although obviously if your coop is the same temperature as outdoors and outdoors sits at 95% humidity for a week then you are pretty much GOING to get that inside your coop whether you like it or not. But that is not usually an issue)