The pH of your tap water is OK for Boesman's Rainbowfish, as these fish prefer alkaline water (pH 7.0 to 8.0 is recommended by most authorities as suitable) so you will have no problems with this fish. [Side note; this species was first introduced to the hobby in (I think) 1983 by our friend and fellow forum member Heiko Bleher, who has discovered dozens of new species in his 35+ years of exploring the very remote areas on this planet. The beautiful Brilliant Rummynose Tetra was named by the late Dr. Jacques Gery as Hemmigrammus bleheri in Heiko's honour since he discovered it in the Rio Negro in the 1960's. Heiko is a great asset to our hobby.]
Water that has a degree of hardness (and I would expect your tap water to be probably moderately hard) contains natural buffers that will work to keep the pH stable. Adding chemicals to adjust it will only do so immediately, then the natural buffering action kicks in and adjusts the pH back to where it was. Eventually as more chemicals are added the buffering capacity is reached and at that point the pH will crash and drop very fast and far. When this occurs, fish in the tank are frequently killed, and even if not they would have been weakened throughout the constant fluctuation as the chemical was continually being added. Such stress frequently brings on disease and health issues. This is why it is not good to use these chemicals with fish in the tank; but it also explains why they are not having the desired effect.
You mentioned the tank being pH 8.2, which suggests there may be something in it that is raising the pH. Rocks that are calcium-based (like limestone, lavarock...) will do this, as will gravels composed of dolomite, crushed coral, or limestone. If you have regular aquarim gravel, it is (or should be) inert, unless it was intended for marine tanks or rift lake cichlids. I would do a major water change to remove all the pH adjusting chemicals.
The addition of filter media to cycle the tank was good, but without a source of ammonia in the tank the bacteria will die off fairly quickly. Fish provide the ammonia, and I personally prefer using fish to cycle a tank when I add bacteria from gravel, filter media, wood, plants, etc. However, you mention a steady ammonia reading so it is coming from somewhere. You should check your tap water; some areas have ammonia in the tap water, and if so, using a good conditioner like Prime that detoxifies ammonia as well as removing chlorine, chloramine and heavy metals will solve this problem. It does not remove the ammonia, it only makes it non-toxic, so the bacteria cycle (supposedly) still functions.