it is better to use a device that is 80% free than one that is 10% or 20% free

Yes! I feel the same way. Each step moves use closer and closer.

The more of these de-Googling articles I read, the more I want to do it myself!

Take a month and mentally prepare. Also over that month it is wise to find apps in fDroid that will fill a need so you don't have to worry about an APK needing some Google stuff.