You could do either. We mainly want to make sure it goes to a landfill.
Probably very low. There are a myriad of ways that small amounts of prions get spread like crows/vultures feeding on carcasses then pooping it out elsewhere, hay or other ag products from CWD areas that deer utilized, mud on truck tires, etc. None of these are really feasible sources of infection because an individual likely wouldn't consume enough prion to cause an infection. It just doesn't seem to transmit very easily from environmental contamination, live deer to deer is the primary mode of transmission.
So there is some research that shows that increased humic acid in soil can reduce the infectivity of prions in soil. While that may help address the environmental contamination issue in areas that have high humic acid, it has nothing to do with deer to deer transmission. Looks like some deer breeders decided that since humic acid reduced infectivity in the soil it must also work if you feed it to a deer. There's no evidence that feeding anything to a deer will eliminate or reduce CWD. Bleach will completely destroy CWD, but that doesn't mean feeding bleach to deer will eliminate CWD.
That's some sort of tumor, it's not uncommon and not caused by any transmissible disease. Growths and tumors freak people out the most, but they are the least concerning from a herd health perspective. I wouldn't eat a deer with a large growth though just to be on the safe side.
