>Reduce power usage during peak electricity rates

This is the only one that requires remote write access, and only when "peak electricity rates" means a dynamic pricing system. But it doesn't actually need full Internet access. Instead, prices can be streamed via data diode to a local processor which calculates correct temperatures based on this information. This calculation should set reasonable limits on allowed temperature, so even if somebody sends false pricing information it's just going to waste some electricity and not destroy all the food.

>Optimize defrost cycles and compressor operation to save electricity

Assuming this means something different from "Reduce power usage during peak electricity rates", I don't see how it needs Internet access at all.

All the other points are monitoring tasks that can be done with read-only access via a separate data diode.

"full Internet access" is a term you brought here out of nowhere and is what your whole faulty premise hinges on.