Ok, I have to say that you are up mighty early for a lich
Be careful with BRS, they have a bias and they want to sell to you. They provide just enough information to pull you in but then they push their products. That said your bullet points are sound.
I have been dealing with household CO2 for a while now and not primarily for my fish tank. I have just recently made an investment in a indoor air quality monitor that has been absolutely helpful in seeing indoor air quality and most importantly CO2 levels. Because my house is pretty old I have no real ventilation, I have to vent the house twice a day using a big fan in the window. I was shocked at the levels of CO2 in my house. I got the Airthings (
https://www.homedepot.com/p/Airthin...01&gclid=CMug3ffC8OsCFRGvZQodLFoBnQ&gclsrc=ds) monitor. It is a bit expensive, but I can vouch for it's usefulness and it is pretty shocking to see the numbers. Perhaps this would be something useful to you also.
Just to note ph isn't always caused by indoor air quality but that it is a very high likelihood that it is.