Does every human on Earth have Anunnaki DNA in them, to a greater or lesser extent?

They are not linear descendents of Anunnaki. There is a more restricted Anunnaki bloodline that keeps to itself and cultivates the heritage quite closely through having an awareness of their origins, so this is not a DNA alteration planet-wide from interbreeding. The downgrading of human DNA by Anunnaki is universal among those outside the bloodline.