What you describe is quite typical; first a high, brain fog lifts, energy for the first time in ages.
Then the detox set in.
To proceed, first of all your selenium dosage is a bit high for this low amount of iodine. 200 mcg is more suited when you hit the level of 50 mg of iodine.
Too much selenium vs Iodine
can make hypo symptoms worse.
No, IMO you did not take too much, but probably your thyroid started waking up. Here is where co factors like magnesium comes in. Also vit C in gram sizes, and a good amount of salt are good helpers in the detox process. Read up on it.
Some detox are to be expected. Mine was hell and did last for 3 months. The feeling of heat shows that the Iodine
is doing a job, maybe replacing fluoride / bromide.
At this forum several have reported LESS detox when taking 100 mg of iodine, this is my experience; as small amounts may only stir things up, but doesnt have the power to push the toxins out. This is one way to do it.
Other ways are to titrate up slowly.
To check if you actually are hypo T or hyper; check your body temperature;