It sounds like it may have gone past the Gallstones
in the gallbladder problem, and is causing pancreatitis. If a stone, or parasites, are in the common bile duct, the pancreas will be doing it's job of releasing enzymes, but it ends up eating itself up. The weight loss, and not being able to keep food down would be an indication of pancreas. People literally starve to death with pancreatitis.
It doesn't have to be olive oil, any oil will work. The purpose of the oil is to stimulate the release of bile. The sour lemon, or lime, or grapefruit juice mixed with it, will cause the vagus nerve to stimulate bile flow too.
He could do the Schultze 5 day liver cleanse. Most likely there are calcified stones, and chanca piedra will help break them down. parasites
will also block the liver, gallbladder, bile ducts, and pancreas.
Make sure the bowels are cleaning out well. The Gerson therapy, with coffee enemas
done regularly, would also help.
Read through Unyquity's forum for the Schultze flushes, and coffee enemas.