Originally Posted by LoosBenz

OK, humor me. I haven't seen anything in your posts where you've actually removed the cables from the battery. So, try removing the cables and connecting the jumper cables directly to the battery posts. Do your "spark test" and if you get the expected spark, the battery is probably ok. If so, clean the battery posts and inside the cable terminal clamps where they contact the posts with sand paper or wire brush. Reinstall the cables to the battery and try to start the car.

If no sparking when attached directly to the battery posts, the battery is defective.