What about Brazil nuts as a source of selenium? I've heard they are a good source.

Yes, Brazil nuts do contain selenium and I have no problem with you eating them. However, they contain the organic form of selenium (selenomethionine). And as I mention in the week 1 module, selenomethionine isn't the best form of selenium for the conversion of T4 to T3, especially in people with impaired methylation. So you need to make sure you still get enough sodium selenate every day, even if you're eating Brazil Nuts. I will know how much selenate you need once I see the results of your hair test. 

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Although selenomethionine raises circulating selenium concentrations, there is no change in thyroid function: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2682996/