Hi Laurie,
Welcome to the forums 
Re the posting difficultes, here’s a post I’ve made previously about how to paste your code in:
And you can upload/insert images by clicking on the
icon, or you can just copy and paste them in.
We’ve got some good articles on powering a project from a battery:
Cold is very hard on batteries, and they often won’t be designed to work down at sub-zero temperatures as it will freeze the electrolyte. I’d recommend keeping your batteries outside the freezer and running a wire in to power your device. It shouldn’t affect the seal on your freezer much.
I’d also suggest taking a look at our recently released Makerverse Nano-Power timer:
Yes, monitoring the battery voltage is the usually way. A fully charged LiPo will be around 4.2v, and dead flat below 3.0v. Here’s an article I found with a quick google that gives some good advice on understanding the discharge profile of a typical LiPo battery:
Hard to say. If there’s enough air and the bag is sealed, and the ice has somewhere else to expand it might be ok. If the sensor gets frozen into the ice it might get crushed. You also run the risk of condensation and ice forming on the PCB, which may also result in damage - it’s not the best choice of temperature sensor for what you’re doing.
You might be better off with a waterproof sensor, like one of the more common DS18B20s:
