Here are a few links I found while researching selenium.
It seems selenite and selenate salts are the ones that pose higher risks of toxicity.
It looks like rats fed 1.5-3mg (not mcg) per kg of body weight suffered no problems short term. Long term effects weren't studied.
This makes me feel a little better about a higher dosage. I did have some diarrhea today, but I attribute this to detox. I'm at 100mg of Iodine now, and haven't taken high dose Iodine (or selenium for that matter) in over a year.
Selenium and Pancreatic Islet Cell Function (this is very very promising for people like me):