It's not surprising those people got worse....intravenous DMPS (and DMSA) and challenge tests are quite dangerous for the reasons you mention. However very very low oral doses (eg as low as 10mg) of both are supposed to be fairly safe according to Andy Cutler. He seems to have researched all this quite thoroughly.
I was planning to follow Cutler's protocol of frequent doses of DMSA and ALA (alpha lipoic acid). He says this is one of the safest and effective ways to chelate so I was very interested in reading your post.
I also think saunas are great to use alongside chelation. I hope you continue to get well.