yeah, it all does sound like typical ammonia signs. Clamped fins, gasping at the top or hanging at the bottom, sore or swollen gills. It's all there.
As Eagles said - keep up the water changes. Keep in mind that if your reading is 0.50ppm and you change 25% of the total water you will only reduce the ammonia by half - 0.25ppm. So keep the water changes larger rather than smaller to be sure you are zero-ing the ammonia. To be certain you can re-test the water after the water change to be sure you've got rid of it all. I hope that makes sense
As Eagles said - keep up the water changes. Keep in mind that if your reading is 0.50ppm and you change 25% of the total water you will only reduce the ammonia by half - 0.25ppm. So keep the water changes larger rather than smaller to be sure you are zero-ing the ammonia. To be certain you can re-test the water after the water change to be sure you've got rid of it all. I hope that makes sense