The best way that I have found for killing pinky mice is blunt force trauma. It is inconvenient, but I throw them one at a time, head first at the cement floor. For them, it's like getting hit by a truck, lights out immediately. Then I freeze them as a means of secondary euth. to ensure they don't ever wake up. This method replicates the "whacking" method used on larger adults but is unable to be done on such small, tail-less animals.

As per bacteria, no, freezing does not kill all bacteria. It can actually preserve it.

Bacteria, and pathogens of any type for that matter, create disease for two reasons.
1. Virulence. This is how much of the pathogen is necessary to cause disease. A highly virulent bacteria would only need small amounts to seed a culture, grow and cause problems.
2. Exposure. Even bland, every day bacteria like Staphylococcus can cause disease if the host is overwhelmed by it.

Where virulence and exposure intersect, you get disease.

Snakes have been documented eating roadkill. They have a pretty good stomach for grossness. But that's not a reason to ignore reasonable discussion on feeding practices. As per stories about food poisoning, we report diarrhea in reptiles all the time. We report regurgitation. Even on this website there is plenty of evidence that certain items can make your snake sick. We blame it on "mystery toxins" but the fact is it certainly could be a simple case of food poisoning. It's hard enough to convince people to get diagnostics done on a sick gartersnake, let alone additional ones to link it to the food they were given. If a human gets salmonellosis, it's "food poisoning". If a snake gets the same, it's because "they're carriers" - not so simple, see 1. and 2. again.

Again, I'm not trying to be super pessimistic about this product. I am just trying to offer an informative discussion.

Ian