DMSA is also active against lead, arsenic, and cadmium. It might be a good idea to do a few more rounds using both DMSA and ALA.
If you get no adverse effects using 100 mg doses of ALA then you probably don't have a mercury problem.

Taking ALA just one dose a day is a bad idea. You might benefit from taking other sulphur supplements though such as NAC and MSM, and eating high sulphur foods such as garlic, eggs and broccoli.