Not exactly, technically. It is rather complicated chemistry, but I'll try. Ammonia is non-ionized and has the formula NH3. Ammonium is ionized, and has the formula NH4+. The pH of the water determines which predominates, and if the pH changes, so will the ammonia/ammonium. The more basic the pH, the more ammonia, the more acidic, the less ammonia and more ammonium. As long as your pH remains acidic, "ammonia" showing in tests will be ammonium. Our test kits do not distinguish between ammonia and ammonium.
I still wouldn't want to see "ammonia" showing in tests, but at least there is no danger and it is decreasing so I think you are likely on the correct road.
To some extent, yes, but this also is not a problem. Here's an excerpt from an article on bacteria I wrote a few years back that will explain it:
The pH has a direct effect on nitrifying bacteria. These bacteriao perate at close to 100% effectiveness at a pH of 8.3, and this level of efficiency decreases as the pH lowers. At pH 7.0 efficiency is only 50%, at 6.5 only 30%, and at 6.0 only10%. Below 6.0 the bacteria enter a state of dormancy and cease functioning. [5] Fortunately, in acidic water (pH below 7.0) ammonia automatically ionizes into ammonium which is basically harmless. And since nitrite will not be produced when the ammonia-oxidizing bacteria are in “hibernation,” this decrease in their effectiveness poses no immediate danger to the fish and other life forms.