Okay, I'll investigate those a bit more tomorrow to see if I can figure out what was going on. Specifically I'm worried about the unshootable stuff more than the target selection for now. The selection algorithm isn't perfect, but having a slightly illogical target selection in a mess of demons is a lot less bad than not being able to shoot them at all :^)
Ideally, I'll figure out something for both issues. Maybe I can add some weighting for aim offset as well, so it preferentially shoots things near the center of the screen.