First thing that comes to mind is that he may have a clogged Gallbladder/Liver. If this goes on long enough it can enflame the Pancreas (causing the Nausea) The malfunction of the Pancreas is connected to Diabetes.
Coffee Enemas, Coffee Enemas, Coffee Enemas. He can do one once a day for awhile until he feels better, he may even get out some Stones:
I couple years or so ago I had a Gallstone Attack, much Nausea and I couldn't eat anything. I felt really sick. The Doctor wanted to cut out my Gallbladder - no way!
So I did lots of coffee enemas and downed some Sunflower Oil and Lecithin Granules and some Epsom Salts (sometimes these cause Nausea but I was desperate) And I got out Stones in the second Coffee Enema. What a relief!