I don't get on with my parents, at all. I live on my own anyway. I am living with my best friend who's parents are willing to adopt me, seeming I'm over 16 is this legal to do so even without my birth parents consent?

I do not know NZ law for sure, but in most countries you are unable to make legal decisions for yourself until you are a legal adult--18 in most places.

So no, you cannot make this legal decision without the input of your legal guardians and their consent.

No, but if they have stopped supporting you, are you run away, or did they give permission to move out.

With an attorney you may be able to show they no longer care for you