The question KBr vs. NH4Br in bleach is a question of cost, availability and how long your washing cycle will be after bleach. In many cases KBr will be much cheaper, and it will likely work just as well. The biggest issue with potassium ions is if you get them into your bleach in larger amounts, they form an insoluble mixed salt with silver, thiosulfate and bromide, which greatly diminishes the capacity of your fixer. If you look at the Kodak 5l kit patent: they go directly from bleach to fixer in order to speed up processing time, so Kodak's patent had to use the precursors to NH4Br. Fuji's patent as far as I remember has a wash step between bleach and fixer and can therefore use the cheaper KBr.
Regarding the nitrate in bleach: many professional outfits process in stainless steel tanks, which are allegedly corroded by bleach. The nitrate somehow prevents this, I don't know why and was never offered an explanation. If you process in plastic tanks, you should skip the nitrate and thereby also avoid gov't questioning "what exactly do you plan to use nitrate for???".
Regarding 1-Thioglycerol: it's a bleach accelerator, which reeks to high heaven, like many of its replacement options like 1-Thioglycolic Acid and its salts. In general it's a bit easier to get 1-Thioglycolic Acid Sodium Salt, because "it's not an acid so we would ship it to you". A somewhat different, but according to a patent preferable option is Mercaptotriazol. This one is mostly odorless and works just as well. AFAIK Tetenal used in in their BLIX for the same purpose.
Regarding amount: The amount is somewhat difficult to adjust, since it sticks to silver, so it gets removed during processing. Adding too much actually kills the bleach, so you are wedged between a rock and a hard place. Therefore professional E-6 process designers performed a smart move: they put the bleach accelerator into the prebleach and designed the process to go from prebleach directly into bleach. This sort of replenishes the bleach accelerator level in the bleach even if you reuse, and at the same time its level stays low enough to keep the bleach active.
Mercaptotriazole should be available from Suvatlar in Germany, and since you are on the American continent, you could check with Formulary or Artcraft. If you insist on thioglycolic something and have a source for it, then please put it in the prebleach and use simple molar substitution.
Finally regarding the Cysteine: I've seen many patents for bleach accelerators, which mention a large range of viable compounds, and I don't remember Cysteine mentioned in any of these. These patents also don't mention a reaction mechanism behind this bleach acceleration, so I have no idea upfront, which compound works and which doesn't. I am not even sure, whether the patenting entities knew, why their soups worked. Conclusion: it's unlikely that Cysteine works as bleach accelerator, but you can always try, since bleaching runs to completion, can happen in room light and can be repeated as often as needed.
