Hi. The shader is not really meant to be used to render individual sprites (not counting the obvious texture page issue, it would also require a custom draw_sprite function that would provide a large enough rasterised area for the "offset" effects not to be cut off). It's a full-scale post-processing effect. AFAIK, people usually get around this by using a big surface instead.
As for the resolution problem, by default the size of the application surface is used. If you need a different one, pass it via the arguments of the BktGlitch_activate function.