In order:
1. Ignosticism isn't about the ignostic being unable to define god. It is about the concept being vague or worse to begin with.
Who's fault is that but our own?
"God" is a possibility, not a fact. The future is a whole set of possibilities, but is not a fact. We humans live in a world that is mostly comprised of possibilities, not facts, because we are not omniscient, nor clairvoyant, and so we cannot perceive our reality as an intelligable fact. So why are we whining that God is not a fact when almost nothing in our experience of existence, is? And since when do we stop asking questions and contemplating the possibilities of existence just because we don't know all the facts?
2. The unwillingness to accept any definition is not part of the idea of ignosticism, which on the contrary demands definitions.
Yes, that is the petulance I was referring to ... this silly demand for definition in a world that is not a matter of fact. Possibilities involve and include many different resolutions that have not yet become manifested or "defined". Every morning we wake up and face a day that is full of possibilities, and therefor is not yet defined. This is a fact of the human condition. What kind of fool looks at the day ahead and decides he doesn't want to consider it's possibilities because they are not defined yet?
3. Neither is ignosticism about declaring the matter of god's existence invalid. I have no idea why you would think that it is.
Willful ignorance implies that one does not consider that which is being ignored 'valid' enough to warrant consideration.
4. No, I still see no petulance in ignosticism.
All that said, I have suspected for some time that your understanding of god, theism and atheism is considerably distanced from mine, to the point that I don't know that you want to be understood about the subject matter.
The discussion is not about what I want for or from you. Only you can decide what you gain from it, or don't. All I can do is respond to the comments I am being offered as honestly and clearly as I can. What you do with that is not in my control. Nor would I want it to be.
I see theism as simply being the philosophical proposition that God/gods exist, and exist in a way that matters (or should matter) to we humans. Thus, I see the nature and existence of "God" as a POSSIBILITY, not as a fact. But as I stated above, most of existence as we experience it comes to us in the form of a multiplex of possibilities. And we then must choose to act on which ever likely possibilities we want to see manifested according to whatever criteria we are using to decide that. (I call this faith, or acting on faith because it neither requires nor demands that we "believe" the result we desire will in fact be manifested.)
To reject a very useful possibility simply because it is only a possibility is, to me, very childish, foolish, and weirdly inhumane. 'Petulant', in fact. And since this is what a lot of "atheists" are claiming they are doing, I find a lot of atheists to be foolish and 'petulant'. This is not to say that atheism is not a viable possibility in it's own right. Because it is. My argument is not with atheism as a philosophical position. My argument is with why I see most atheists choosing it.