Hello and welcome.
I hope there will be some people knowledgeable in your area of work along to comment later.
3b. There is no mention of a requirement for work experience in the listing.
3c. Who were the organizers of the NGO? This may have quite a large bearing on whether or not your experience in India would count as being in a comparable labour market.
http://glossary.immigration.govt.nz/...experience.htm Your current situation (working or not) could mean that this matters quite a lot.
Then, if your Diplomingenieur does indeed turn out to get a Level 7, like a bachelor's degree, maybe it does not matter that the Indian experience is not after your master's qualification (because it was after the bachelor's degree). If. But notice, the work experience has to be 30 hours per week minimum, in order to count as full-time. And it is likely that both the work experience and the master's qualification would be investigated very thoroughly as they were done simultaneously. Have you looked at the list on the INZ website of qualifications exempt from assessment?
3f. Your written English comes over well. How do you get on when talking to English speakers face to face? Do they understand you, and do you normally understand them without hesitation? Have you looked on e.g. YouTube to try listening to NZ voices? NZ is an environment where very few people speak European languages, and all the effort will need to be on your side. If you got to the stage of an interview, and your English caused any lack of understanding in either direction, it would be enough to lose you any chance.