Never charge it to 100% and never leave it plugged in overnight. Avoid if at all possible discharging below 20%.
Apple's battery care recommendations had to balance convenience and device run time vs battery longevity.
They have zero incentive to keep a battery healthy for 4 years or longer.
Everything you said is true. I used to have some bad battery ocd. I gave that stuff up and just charge to 100% every night. I had an app on Android that warned me once the phone had charged to 80%.
iPhones charge so slow that it’s hard to baby them as much as an android. Not charging to 100% could mean the difference of having to charge before you go out after work, or your phone dying when you need it most. If the phone was junk after the battery was used up, everyone would baby them. In your case you have been taking as good care of the battery as you can, and your reward is you’re saving $50 by not having to replace your battery. To me, it’s not worth it and I feel much better now that I just use my phone and forget it. I will do what I can to always keep it above 20%, but the days of waking up and charging my phone to 80% to avoid charging it overnight are over.