I can't answer all the questions yet, but I want to address the issue of wholewheat bread. I have been reading the other topic is which someone referred to an improvement in their health when they stopped eating wheat.
There is a genuine allergy to wheat. But as far as I know while such people cannot eat wheat, they may eat other grains without problems. However, there is a disease, called celiac sprue, which causes gluten intolerance. Gluten is the protein found in grains, including wheat. Anyone who has celiac disease (also called gluten intolerance) cannot eat wheat, oats, barley, or any grain high in gluten. They can usually eat rice and corn.
Celiac disease brings with it problems with malabsorbtion. Those afflicted have difficulty absorbing all the nutrients they need which can, in turn, lead to other problems. It also causes gastrointestional disturbances such as gas and bloating. I am familiar with the disease as I have a good friend who has the condition and have known others with it. Gluten intolerance is not an allergy as such but a medical condition that some say is way under-diagnosed. There are probably more people who have it than anyone realizes.
While I need to do more research on allergies, I do know that there seems to be a genetic predisposition to allergies in some families.
