I still have the sensors and still use them. They rarely miss an opening/closing, although I have one that I think may be playing up a little. They are cheap enough to throw away and replace, just haven’t got around to it yet.
Range on the Sonoff bridge is … limited. I have two of them - one at the front of the house, and one at the back. With the two of them, it covers the whole house, including ground and first floor. If you get much more than about 5 or 6 metres, then you are doing pretty well. The best thing about the Sonoff is that you can have multiple of them, and they are cheap - just get as many as you need to provide adequate coverage.
I must admit I never attempted get anything working with the stock Sonoff firmware. First thing I did after unboxing then was flash them with Tasmota.