If he is losing weight, possibly a high-calorie liquid food like Ensure Plus or Boost would be tolerated and help him keep his weight up? There are also high calorie puddings, ice cream, etc. that you may be able to purchase at a hospital or medical supply store. Enlive mentioned above comes as a boxed drink and I think has a couple hundred calories. Could the dizzines be from dehydration?
In terms of binding foods, I have heard of BRAT (Bananas, rice, applesauce, toast). I don't know how well these work in the context of a flare. A liquid diet will help healing probably but won't stop the D in the short term.
Being so soon after surgery, he is already in a weakened state...Was he in the hospital, is it possible he contracted C. difficile? Did he take any antibiotics recently? Could he be anemic? I agree with the above post that you should probably contact a doc. Hope things improve soon.
July 2007 Drug-Induced Liver Injury
January 2008 Crohn's Ileitis
Entocort, Enteral Nutrition, Omega-3 (Flax Oil and Fish Oil), VSL#3, Vitamin E