The salt needed is far much than in cooking; like half a teaspoon extra, daily. I like it in my water. Read up about salt loading, also http://www.watercure.com
The salt is crucial as the Iodine will cause some bromide excretion, and the chloride in the salt will make this manageable. Forget everything you learned about salt, is my advice :) start again.
The magnesium oxide is not good, as it is almost insoluble; go for citrate or malate or glycinate. Easier utilized.