Hover thrust

Hello everyone! I recently assembled my first drone and I’m trying to perform flight tests. How precisely do I have to set “hover thrust” parameter to hover with released sticks?

I understand that this parameter is necessary to set hover thrust after switch from “altitude” (or “position”) to «stabilize» flight mode but why the flight controller cannot control altitude in “altitude” or “position” flight mode without this parameter?

If I make a cargo drone, will I have to set new value of hover thrust before each flight depending on weight of cargo?

For reference: my drone is equipped with 4x BR2212 engines which have to provide 535 g. of thrust with 3s battery and 8045 props. Actually I’m using 4s battery so thrust should be higher. The drone weight is around 800 g. I expected that hover thrust for my drone should be less than 50 % but actually, it descends even with 60 % hover thrust.