To try and answer your points.

1) This is a problem in the US and many other countries. People resist change. USGBC goal with LEED is to be market changing. To encourage people to change what typical business means.

2) Sometimes this happens. When submitting for the credit an explanation should be added to explain why the different calculation is just as good as the US version. They may respond with a request for additional information. Converting the calculations to metric units would not be a problem.

3) I'm not sure on this. What credit are you referring to? Like SSc1 refers to the 100-year flood plain. I'm sure local weather data can be used to calculate the elevation of the 100-year flood plain for your site.

4) It's possible that they will accept this if the water is treated on site. Since this is not a typical location expect the reviewer to ask a few questions to verify water quality and documentation.

5) Read thru here and see if your question is answered.
http://www.leeduser.com/credit/NC-v2.2/WEc1.1-1.2