I'm gonna answer 6 first...
Quite frightened, but intrigued - I'm gonna stick with the intrigued, it'll be more fun.
1. Well, a normal adult human has about 5L of blood, so how many humans can we fit in a cow? I guess that depending on the size of the cow somewhere around 35-40L sounds reasonable to me.
2. Skipping cuz I know nothing about the Pope or the Vatican beyond what I've read in novels.
3. Yes, brain damage can result in temperature instability. It does depend on what parts of the brain are affected. The hypothalamus is part of the brain involved in normal temperature regulation. The brain stem itself also plays important roles in maintaining the body's temperature (along with breathing, heart rate, all that good stuff). So if these areas are injured by lack of blood flow, severe infections, actual traumatic damage; or if the parts of the brain responsible for relaying signals between these parts and the rest of the brain are damaged, then there can definitely be high (or low) temperatures that are not related to actual infections and are just because the brain is not working right.
4. The blood is very rich in nutrients and pretty much all the essential elements of life. The proteins, amino acids, fatty acids, sugars, minerals etc... Hemoglobin is also in there, of course...quite important. Not all animals do make hemoglobin perfectly well - as species baselines, yes. But just like in humans, other species do have the occasional disease/disorder that prevents them from producing "good" hemoglobin. Humans have thalassemias, anemias from dietary deficiencies, sicke-cell anemia, and a really cool one called porphyria - which is a disorder caused by abnormalities in the chemical steps leading to the production of heme. This disorder is hypothesized to be the original origin of vampire legends. These individuals are often pale, sensitive to sunlight (with resulting rashes and blistering) and also known to occasionally drink blood to supplement some of the key elements they are missing. There was a European royal family that had this running in their gene pool at one point - can't remember which ones though...
Jill
