So I spent the better part of today trying to grok the PorkPi files, and simplify them for my own use. It didn't help that this was also my first experience with Python, but I had enough background with some other types of scripting that it was pretty easy to pick up. Also a bunch of temporary hurdles popped up, for example, with getting a service account set up and with using the oauth2 SignedJwtAssertionCredentials method because it is no longer supported in the current oauth2client package, which is what is installed by default unless you specify an older version. So I burnt some time figuring out that I had to update the code with the newer ServiceAccountCredentials method.
In the long run, trying to simplify PorkPi for my own use was taking quite a bit of time because I was trying to both debug and learn on-the-fly. So to get basic functionality up and running, I ended up putting PorkPi aside, and just writing my own basic ~20 line script. All it does for the moment is simply logs temperature and humidity values directly to Google Sheets. But I'll continue adding to it to start controlling the relays that turn the fridge and humidifier on and off. Also, there's a bunch of neat stuff like all the watchdogs and error/exception checking in the PorkPi package--I will eventually add some of that in to my own version for polish and resilience.
Thanks again, hjbct, for your generosity in posting this! I'm taking your suggestion about load cells, and just ordered five load cell+HX711 modules on Aliexpress. They are super cheap like just US$3.13!!! If you are interested in the BME280 sensors, you can get them on Aliexpress for < US$3 so they are supercheap, too.