A person might tolerate a dose while "reloading" a mineral but then only need a much smaller maintenance dose.
Mercury affects the movement--transport--of minerals. Healthy people might tolerate more generous doses than a person with an Hg problem.
There are plenty of posts in CZ from people who took doses too high for them and regretted it.
My impression from your post is that you need more information before taking big doses of iodine.
From my years in the heavy metal detox groups megadoses of Iodine have not often been reported to be a big help. There are other interventions that are more commonly reported as quite helpful.
Thyroid is only one factor that can affect weight. Heavy metals affect energy production, mitochondria, catecholamine neurotransmitters (inattentive ADD, etc), steroid hormone imbalances, various medications, etc.
You may need to change your diet. It is not just about how much you eat but about food groups, etc. Dr Mark Hyman is interesting on the subject of metabolic syndrome. I don't have a link but this might get you started. http://www.youtube.com/watch?v=wkxk7nod33o