If you have a limited window of time to do the cleanse, the best you probably can do is to keep going and you get out of it what you get out of it.
The food certainly will shut down the cleansing activity, but it will start again.
Hard to say why your stomach would cramp up.
Seems that plenty of lemonaides and water should prevent it, although it sounds a bit like dehydration.
Possibly the performance demanded more fluids.
One thing you can take from this is the experience and next time you will have that with you.