1st off welcome. I'll try and address some issues and then it's probably going to be a mass execution of medi-cal with some vet tech chirping in on how good it is
The part about being under a car
alarm bells ringing, I work on cars all the time and as such I have engines laying around, I thought my baby had been hiding out inder one when she was covered in what looked like the crud on the outside of a bad engine, turns out it was dried blood from an absess under her tounge and bleeding gums from tarter build up. I would get some of hte tarter remover additive and put that in the food immeadiatly, I thought it was a gimick and found out to late it really really works. Look under the tounge and by the gums for any bleeding. If it's not what I describe then I'm sorry, but I really thought my angel was covered in grease and to my shock the problems just got worse and worse. Externally there is not a lot to do except bathing (if tollerated) with non medicated shampoo. Internally, well where to start, I guess probiotics may melp replenish her gut with enzymes that may have been washed out of the system. Next is the good old subject of food, the one your giving is not helping, cereals are known to be the biggest allergins and medical has it all. I would look for a simple diet with as few protein scorces as possible, if no change in a week change to another protein, and again untill you have found what you are trying to aviod. A friend of mine swapped to a venison based food as it elimanted all the problems in one go. Now she knows it was 'something' in the food, in a few months she will revist each protein one at a time and find out what it was, for the mean time she is happy the allergies are gone. So my only sudgestion is have a look at somewhere that gives you the breakdown, try and find a food that is obtainable and has gotten rid of the cereals, or go you could try homecooking for a week, something like emu and rice and seeing if that helps (something that would be not included in the previous foods). I'll open the floor to the others as they have loads more information than I could ever hope to give. Good luck and keep us informed.
P.S. pictures 'well or not' are required...............regularly.