Those symptoms are all about the liver! :) Check out the liver notes and all the links to sensiblehealth.com and liverdoctor.com, you'll see your symptoms listed.
The reason for the maple syrup is:
1. minerals (that's why grade B)
2. slow down detoxing. Sugar stops detoxing so you don't detox as fast as a water fast.
3. Energy - sort of
Some people like diabetics use molasses instead.
You can use Stevia no problem, then it wouldn't feed candida and would be a much better fast.
The problem is overdosing on lemon juice is hard on the liver and your poor liver is already weak and stressed as it is!!! You neeed a liver-friendly fast, which would be carrot/apple/beet juice. :)