Living in the cold north, bulk loading and regularly storing stuff in the freezer, I've come to know a bit about freezing film.
Humidity will come 90% from condensation. The ambient air is rarely a problem. What happens is that when something cold goes back to a warmer environment, the humidity that's in the air will settle on every surface that's cold. Warm air can absorb a lot more humidity than cold air. So, you want to avoid the water from coming in contact with the film.
The best solution is to put the bulk film, or even the entire bulk loader in a plastic ziploc bag before putting it in the freezer. When you need some film, you have to plan ahead, so the night before you pull the bag out of the freezer and very importantly, you leave it inside the bag making sure that the exterior air never gets in contact with the interior air. The next morning, when you pull the loader from the bag, it will be very dry and ready to use.
As for the cassettes, like everybody says: put tape on both sides of the film!
If not, it's just asking for trouble.