Why? A little piece of ingested bedding isn't going to harm it any.
Depends. The person below has the right idea.
Yup, we would need to know the weight of your ball before making any guesses. Hoppers are a very small meal, so unless your ball is a fresh hatchling, chances are you'll need more than a hopper. 3 weeks isn't a long time to go without food, but I often feed a couple smaller meals following a hunger strike to get their stomachs used to having food again.