About your 3rd and 4th questions...
3.) The brain has its special area for just about everything. I think I've heard of one that's responsible for setting the body's temperature - normal or feverish. If you simply assume that's true, and that particular area is scarred... Well, why not? Maybe only the control over the sweating is gone so that the person suffering from the scar developes a fever whenever in a warm climate or doing sports...
4.) Blood contains everything the body needs since it is the body's infrastructure. It contains all the minerlas (especially ferrum in large quantities), amino acids, fatty acids... even most cells of the working immune system. And thee cells can be taken into the body of the animal licking the blood, I suppose. At least the same trick works for babies who're breastfed. Although I doubt that the hemoglobine is taken into the body as a whole. Every Mammal (reptile, amphibian, fish, bird...) can produce hemoglobine perfectly well - or it would die. It's that simple. But the amino acids needed for the hemoglobine - well, they can be used for sure. And (since I don't know which ones are involved) there might be a few rare ones involved.
