"Soon after taking my DMSA/ALA dose (50mg DMSA, 100mg ALA) my stomach goes gurgly for a little while. Not always. Every now and then I have a short bout of diarrhoea from an unknown source, say maybe once every 2 or 3 days. "

Some people would say that mild diarrhoea is good for detoxifying your digestion system. If it is severe though, or you feel that you are losing too much of beneficial minerals, then perhaps you should cut back on your vitamin c intake? Didn't you say you are taking a crazy amount of vitamin c, around 20 or so grams a day? I take 2 grams a day of vitamin c. Imo that amount is plenty.