WOW this is getting complex now. I think I'm beginning to understand the scope of the question. I'll try and answer as best I can.
1. The fish poo in the gravel bed does not increase the amount of ammonia present in the tank. In other words, once it's there, it's there. It's the biological activity of the fish (and or decomposing organics), which continually produces the source of ammonia.
2. The ammonia that you are measuring in
ppm is present in the water column itself. The higher the concentration, the more stress on the fish and the longer the cycle will take. This is because the size of the nitrifying bacteria colony will establish itself based on the amount of ammonia present, and you'll need a massive colony to feed off the ammonia. Doing water changes from the water column alone is beneficial for the cycling. Also,
IMO the classic cloudiness after some tanks cycle is due to a higher than needed bacteria colony being established, and a portion of that bacteria dying off. Hence, the bacterial bloom. Gravel vac during the cycle and you can create the same thing by disturbing and killing the bacteria in the gravel which as Tankgirl says, is tenuous.
3. Sponge filters and bio media in your filters are the best place for harboring the nitrifying bacteria. Water is being constantly circulated through these areas and thus are constantly being fed.
HTH