mercury is always a good bet when there are multiple disparate symptoms such as yours. the thinking put forward by doctors such as dietrich klinghardt is that parasites are a vector of the mercury poisoning and may also serve a function to sequester some of the metals.
pain in your left abdomen could be stomach, pancreas or in some cases referred from gall bladder stasis.
your information about sulfur was half correct. if you read dr. cutler's book carefully, what he says is that mercury toxic people skew either one way or the other as far as reactions to sulfur bearing amino acids. some people will feel a whole lot better on sulfur and some people will feel a whole lot worse, but rarely is there any balance.
my experience is that people who are most sensitive to sulfur are the most toxic. the only good news there is that this is providing diagnostic information for you, the bad news is that it is a long and difficult journey. keep in mind also that current thinking says there is probably more than just one type of metal poisoning. cutler's information is awesome, but keep an open mind toward other therapies as well.
look into saunas, Montmorillonite clay, alginate. hopefully supplementing b12 will be a good start.
were you taking lipoic acid by any chance during your vitamin binge? or was it just the NAC.
citric acid and acetic acid( vinegar) are also weak chelators and can stir up metals.