The reason for the light roast and for boiling the coffee is to get more of certain acids out of the brew. These acids are what, we believe, causes the liver to produce more bile and to shed more of the stored fats containing cholesterol .
To have different reactions to the enemas are normal for me too and I think for everyone. Why? I would say that it is a complex question with very many parts to it. Your mood, how relaxed, how irritated your intestines are, how empty there are, etc. are some of the things I can remember at the moment. I am sure there are lots more reasons.
I hope this answers some of your questions.