You are a bit overly concerned about this. A large hopper could doubtly do any damage to a snake, and even still, many many breeders feed live to hundreds of snakes without a single issue.
Here's my theory. The more you hover and watch the snake with the lights on, the more prone the snake is going to be nervous about eating and possibly cause problems in the actual feeding, which may cause the snake to get bitten.
Also, 3 weeks is no big deal for not feeding a snake. Many ball pythons go months without food and no ill effects. Good thing to get him eating though! :]