The high hair mercury level means that your body was excreting plenty of mercury. I guess you were taking plenty of ALA before this? Those who are most mercury toxic are those who excrete little mercury. Being able to do a 13 day round at a high dosage with minimal side effects means you probably already got rid of much of the mercury.

Don't increase the DMSA dosage too rapidly, as it can cause diarrhea. Imo the max dosage for DMSA should be around half a mg per pound, even though some say to take up to 1 mg per pound. DMSA might be what caused the bloating you experienced. NAC can also cause digestive side effects. DMSA is much less toxic than DMPS,however it is still quite a bit more toxic than ALA. Also keep in mind that DMSA does an even better job chelating lead than mercury(it also chelates cadmium and arsenic) so any chelation symptoms you experience when increasing the DMSA dosage could be due to mobilizing these other metals and not so much from mercury.