Sorry Skuzzy, now you want us to be gentle with the new guys. Ok.....
That ballistic calculator is missing altitude, air density, temperature, total G, horizontal acceleration G, true airspeed, bullet (drift\jump\yaw). It is missing the relationship between the fuselage level lug line, relative bore line and gunsight line of sight when parked on the spawn point. And flight path when testing in auto level.
Some of this can be minimized by shooting sitting at the spawn with your engine off. You will have to use all three parameters of the .target command to line up the offline target with the center of your gunsight. Or you can observe all of this by flying auto level at sea level, 7k, 15k, and 20k at about 300-350IA to see gunnery at many of the altitudes you will fight in the game.
The offline target is a better tool to observe your convergence choices at range because you will see most of the physical factors programmed into gunnery in effect for Aces High. Along with their differences between different rides.