Headcanon is something you think of as fitting to a character - for example some people headcannon their fav characters as being ace or bi or they think they'd have certain habits due to some onscreen quirk in filming (i.e anakin in the prequels wears black/dark clothing because he's from a desert world originally and is thus always cold).
that kinda thing
Desgusting
ah depends sometimes, when I have the urge I tend to concentrate more on my art - or I get too in the zone, though I usually have some audio commentary / music playing while I work tbh