I don't know about sulphur but I can tell you ammonia tests can be pretty inaccurate, it is good for reference if it is abnormally high, but there can be results that show low ammonia despite very high levels in different organs of the body.
Example, some people have ammonia build up from liver and kidney issues, and infections of the digestive tract. This can be shown with higher amounts of ammonia in the urine, it is an a normal spot of ammonia detoxification for the most part so easier to track, however supplements can also raise ammonia levels in urine among other things so be aware of that too. There are other infections that can cause ammonia build up in other organs which can be much harder to catch though.
In my own experience it is well thought but not proven that ammonia is a huge issue in lyme disease, specifically ammonia in the brain, though a test may show elevated ammonia in the body it is harder to find the levels that could be specific to other body parts.
Why is ammonia and sulfur an issue in your case? I do not know too much about testing, but plenty in ways to de tox it depending on the cause.
Let me know and I could give you some good ideas
Todd
p.s. I don't mean to imply test is not worth it, I think its excellent in getting a better idea of what could possibly be going on inside.. Just be aware that using certain vitamins and supplements can give false high levels, and that low ammonia results may not be showing the whole picture.
Ammonia is urine, sulfur can be urine too but I don't know how the blood tests check either of them. Usually a chelating agent is used to push it out and then test the amount in the urine.