First time freezer jam questions

I made strawberry freezer jam today with Certo pectin following this recipe: https://www.kraftheinz.com/surejell/recipes/518933-certo-strawberry-freezer-jam

It's my first time doing this and I have a few questions! How can I tell whether the jam has set and is ready to go in the freezer? Should I leave the jars out for 24h, longer, or shorter and how do I know? Can I transfer jam from one container to another? I used a plastic takeout container but half the container is empty air since the jam only fills half the space.

Thanks in advance!