I've been trying to call up the form to check these points, but at the moment, every time I get the front page of the form, then everything freezes up. Grrr! So this is guesswork, and maybe someone who has gone this route already will cut in, from their experience.
About the departure date question: I believe this form is for a whole lot of different kinds of temporary work visa, and for some of those kinds, the person would indeed be intending to leave again, whereas in your position, you don't. You might put a year's time, or you might put 'indefinite', or you might ask INZ. Anybody out there, what did you do?
I guess that "Family Work Instruction" probably refers to the Operational Manual. I can see "WF Family Stream Work Instructions", accessed via
Temporary entry class visa » Work visas » WF Family stream work instructions. http://www.immigration.govt.nz/opsmanual/index.htm