I hven't heacrd it spoken. It is good to have a good vocabulary.

No. Why do you look askance at me? Why are you looking askance at me? I can safely say I've never used it in writing or in conversation. I've never heard it used by a fellow native speaker either. You might find it used in some more formal pieces of writing.

It would be more usual to say, "Why are you looking at me like that? Is something wrong?" or perhaps, "You're looking askance at me - is there a problem?" Askance is not often used in conversation. It might be used to refer to a situation later: "Well, I could see he was looking askance at the idea, so I asked him what was wrong."