You want to play with mag to suit your eye and your scope.
Generally 10 max.
You want to see the longer targets but the more mag you put on, the fuzzier and blurred the short range becomes.
You have 3 potential bands or zones of focus that will immediately tell you which zone the target lays.
You want to focus the scope so the 45 is JUST blurred but essentially shootable and the 40 is clear or just starting to blur.
That's Zone 3 sorted.
Zone 1 will be close stuff and will also be blurred.
Zone 2 will be the zone that you will see in sharp focus
SO you can know the EXACT distance where each zone transitions so this gives you a rough idea.
You need to mess around with mag to see which gives the best idea of image at 40/45 and what gives the best possible close range image - its the ultra close stuff that will be the issue for you.
Dig out any stuff from Brian Samson.....He knows his stuff and you will learn a lot technically which you can try in the field.
Very fine rets with multi aim point points will help you with your aim points. I find Mil dot is too big and you need mil with half dots too. I like the MTC SCB Christmas tree ret with a floating + cross hair.
In a battle of wits I refuse to engage with an unarmed person.
To one shot one kill, you need to seek the S. Kill only comes from Skill