There are things like this for artillery, sniping, and such. But when would you have time to do this in a fast bombing run? Probably why I've never seen one for aircraft in real life. The thing your looking for is the backup bombing sight. That thing that looks like a spiderweb on the hud. I hope to find some real life data charts for it on the internet one day. If you wanted to use a calculator, you would have to do this before the mission, at base, as your planning your attack. Then hope that you can get near that situation in the real battle (probably not). Too many nasty surprises always waiting to mess up your plans.
As for realistic values, I know they are constantly working on their missile FM. Not so sure about their 20,23, and 30mm shells, but they seem to be modeled well.