Malabsorption issues after Whipple surgery

My husband was diagnosed with pancreatic cancer in November of 2006.  He underwent the Whipple surgery at the end of November.  For the first two years, he had no real problems.  He maintained his weight, but was diagnosed as diabetic as they had taken 2/3 of his pancreas during the surgery.  At the time of surgery my husband was 220 pounds.  Two years later, he was around 190.  Today, my husband weighs 140 pounds.  He has chronic diarrhea and feels tired all of the time.  He takes Creon a pancreatic enzyme to help with absorption.  He also takes 14 Imodium a day with no relief.  We have been to a GI doctor at KU.  We went to the Mayo clinic this summer.  Everyone has a different answer to the problem but nobody has found a solution.  We have tried a gluten free diet, a low fat diet, a lactose free diet.  They all seem to work for a short time, but eventually the diarrhea comes back.  Now it doesn't seem to matter what he eats.  We are not sure what to do or who to turn to.  He is sick of being sick!!! We need help but don't know where to go.  Does any body have any suggestions or experience with these problems?