Thanks for being the voice of reason (VOR) and advocate of the KISS principle. The videos and tables are nice, but on an ST load range D trailer tire the result is nearly always the same, 60 to 65 PSI cold if your Airstream is loaded for adventures on the open road.
It's so simple. You know the gross weight of your trailer. Divide it by four (if you have two axles). Look at the max load and the recommended pressure embossed on the sidewall. Voila, 60 to 65 PSI!
This dictum is not true for the folks that are running LT load range E tires, but that's another thread unto itself.