Corn snake people feed partial pinkies to hatchling corns that are too small to eat a whole pink all the time. There is also a theory that just making a few holes in the skin allows the snake's digestive juices to penetrate faster thus making it a little safer to feed a prey item that is borderline too big. I've heard that one of the dangers of feeding too big of a meal is that it does not get digested fast enough and the snake will regurge whatever remains when it begins to spoil in the stomach, but I'm not sure this is 100% true.

There will be no harm in cutting they prey item in half. It might get messy, but I think as long as the snake eats f/t in general, it will end up eating at least part of the meal even if some guts get squished out. There is virtually no mess if you just cut the head off, although this is obviously not an even division and since snakes go for the head it might not take the body part.