The ESR and DCR are mostly dependent on the package size of the component itself and thus determined entirely experimentally. They are usually on the datasheet and they are one of the deciding factors that goes into choosing the component that goes on the circuit board.
Theoretical design of an SMPS is not the greatest idea since they are so fragile. Theoretical design just doesn't take everything into account properly such as temperature, altitude, frequency, and so many other things.
There is no industry standard as far as I know. You should not need to be too concerned by the current density in the copper. What is important to you as a designer is the DC resistance of the inductor as this will give losses resulting in heat dissipation in your inductor, a too high series resistance and it will get hot !
Another VERY IMPORTANT, perhaps even MORE IMPORTANT property of the inductor is the saturation current. What current can it handle ? If the current rises above this value, the magnetic core of the inductor will saturate and the inductor will start to behave like a (low-value) resistor. The inductor will not be able to store more magnetic energy.
Usually and fortunately if you select an inductor with a sufficiently high saturation current, the copper windings will be able to handle that current :-)
A really great walk-through on DC-DC converter (Buck topology specifically) design calculations can be found at this Microchip Technology's web seminar slideshow. The seminar covers these important topics:
You need to know things like the input voltage, intended output voltage, acceptable input and output ripple voltage for your system/converter IC, and current requirements, as well as the switching frequency of your DC-DC converter IC.