There is little proof and not much research about low level mercury poisoning. If you only had 2 fillings for ten years than your exposure would be 30 times less than mine.
ALA is recommended by AC Hall cutler. DMSA may or may not cross the blood brain barrier. DMPS is dangerous and doesnt cross the blood brain barrier. Eating foods high in sulfur, such as meat, is recommended.
Aluminum makes mercury 50 times more toxic so it in all its forms should be avoided.
Mercury may not be the cause of all your symptoms.