"Sorry I'm too brainfogged and tired to read this whole thread but.. i think the main problem is: how do we REALLY know that its the mercury that is keeping us sick and not something else? There really should be a good test for this but there isn't.
"

If you chelate with both ALA and DMSA it will address heavy metal toxicity for several different metals. It is hard to know what the primary cause of illness is, however ridding your body of toxic heavy metals is a good idea anyway.

Both ALA and DMSA rely on sulphur. If you are sensitive to other high sulphur foods as well(eggs, broccoli, garlic, etc.) then you might be deficient in molybdenum. You could try taking a molybdenum supplement 500-1,000 mcg a day and see if it helps.
Make sure to eliminate sugar(and fruit) and alcohol, and try eating few other carbs for a few weeks and see if you feel better. Replace the fruits with low carb vegetables. Sugar and alcohol are the worst things you can eat as they promote candida overgrowth.