Generally speaking since Iodine is water soluble taking too much means you will simply pass excess in urine. Having said that, taking Iodine without the required selenium can cause problems.
Last time you tried, where you taking any of the cosupplements and if so how much selenium and in what form?
The Amalgams are pretty toxic but you can do a lot to offset and possibly overcome their toxicity by taking ascorbic acid/sodium ascorbate to bowel tolerance.
I dont think having a doc guide you is essential IF you have taken the time to learn and understand the complex relationship of the nutrients you need and take. There are so many places to get lab work done without a doc the main reason to tap into a doc is for their actual clinical experience. That being said you must make sure your doc understands the intricacies as well for if they dont relying on them could be worse than going it alone.
How do you know if a doc is qualified? Comes full circle back to you and knowing what your doing which ina round about way almost negates the need for the doc.