"Those were blood test results from December and end of January. This time, I got a hair test that shows high level of Iodine and selenium. Both of them are at least 10 times the highest value on the reference range."
On the other hand, you have said,
"I have never taken selenium more than 400 mcg/day, and I usually supplemented 200 mcg/day for 4 months. My serum selenium level was still within the reference range, although on the higher end."
I do mineral analysis for people. Ten times the highest value on the reference range is not within the reference range. So what you are saying makes no sense.
I learned about selenium toxicity by reading my Merck Manual. I have no link to furnish you.
I suggest you do some research on your own. You will have to provide consistent information to get realistic help from people here.