1) I haven't tried myself, but it's very likely that if you tried to concurrently use another software for the Wii Remote, this other software has caused your issues.

2) Calibration is not needed and shouldn't be performed unless the shape of your room differs significantly from a normal room. The default values are already optimized for all common cases. Please note that if you don't carry out calibration correctly, you'll leave Remote Buddy's Wii Remote driver with a stack of wrong values, which can lead to unwanted results. Therefore, it's best to leave this setting alone and - if you've used it without any real necessity - reset it back to default values by clicking on "Reset to defaults".

3) The setup is pretty straight forward: open Remote Buddy's Setup Wizard and follow its instructions to pair the Wii Remote. That's all there is to it. Once the Wii Remote is paired with Remote Buddy, it just works. No further setup is required. And as previously mentioned, no calibration is necessary.

4) No stability issues are known.

Best regards, 
Felix Schwarz