You are right. Although the way I was talking about is |(2+10)-(1+20)|= 9 Seems like I coincidentally created some example lists that all worked with this method!
And the algebraic reason would be the presence of parenthesis. |(a+b)-(c+d)| != |(a-c)|+|(b-d)|
Chill out my friend. We use FOSS and privacy respecting things to make our lives easier and more enjoyable . Don't stress yourself. If you need to do something then do it. No need to feel bad.
Something is always better than nothing. You've done so much in terms of better privacy and using FOSS so you're doing great and better than most people. Just live your life and improve things step by step.