My understanding is that 2 & 3 are problems with the original (20kWh) Leaf model. Which possibly led to a rumour about the 40kWh models, that the OP has.
My Leaf from 2019 has 100% battery health and I always charge it to 100%. I almost never use fast charging though since it is a commute kind of car.
Is that the health reported by the car dashboard, or by LeafSpy? The dash has some wiggle room in its 1-10 display an IIRC it will display 100% until the SoH is below like 90%...
Obviously they are reporting the dashboard number. The first bar drops at 85%. For a 2019, it is probably getting close to dropping its first dashboard bar.
After 25 years in the industry I should know that there is always someone that have read more forums and researched more :)
Either way, the car is 6 years old. At this rate the battery will still be pretty fine when it is 15 years old and ready for retirement.
Never charging it above 80% is not worth the hassle. It is like never using your left hand for the fear of hurting your left hand. You are crippling your car by overthinking.
My Leaf from 2019 has 100% battery health and I always charge it to 100%. I almost never use fast charging though since it is a commute kind of car.