Kim, the KMR may make the runs worse right now. I would warm up some baby food and dropper feed that and some of the Gatoraid to him. You know how your stomach hurts sometimes so bad that you don't want to eat but you know you would feel better if you did. I would force a small amount of warmed up baby food. I bet his little bum is sore too.
You can also take towels, blankets, whatever and warm them in the dryer and wrap him in those so he can get warm.