Its really good that your body reacted for iodzed salt, and you got everything out. You didn't say how long ago you left coffee, cigarettes, alcohol and sugar? I always need at least a week without vices, and at least two or three days with a light diet that doesn't include Sugar or spices. If you start off immediately after your normal diet the symptoms are likely to be stronger.
First three days without food are usually quite hard and headache and nausea are quite common. For me bowel flush has helped. However, I wouldn't go on either after as dreadful experience as you had. Even though fasting is beyond common sense, I think its good to use it before you risk your health or feel too bad.