Throttle body adjustment

Good Day All,

The short version is- does anyone know how to properly adjust the screw settings on a gen 2 throttle body?
picture attached
I see three adjustment screws, labeled in the picture 1, 2, and 3. Can anyone tell me the function of each. Also, there is the throttle position sensor on the other side- is there a trick to properly installing or calibrating that?

Reason I'm asking is I know they were fiddled with by a mechanic who worked on the vehicle and now the only way I can get the engine to idle under 1k rpm is by having screw 2 set almost completely clockwise, but then the engine misfires constantly. Like 2 times a second. I have a replacement idle throttle control valve on the way, but I have suspicion to believe that's not even the issue.