In normal operation, you would be feeding reverse current through the device, so the Absolute Maximum Rating would be 15mA; the line on the reverse-voltage graph stops at 10mA, but it probably extends pretty straight up to 15mA. Not that one should operate the part there, but one probably shouldn't worry if current gets up to 11mA.
On the other hand, in most cases there's probably not much point in driving the thing with more than 1mA. The graph suggests that the voltage drop will be pretty constant provided there's at least ~0.4mA flowing through it, but the voltage drop falls off very rapidly below that threshold, so one needs to ensure one is operating safely above it. To allow for part variations, 1mA seems like a good safe operating level. The only time I can see usefulness to going above that would be if one has a load whose demand might vary e.g. from 0-8mA. In that case, one might drive (part plus load) with 10mA and figure that the device would have 2-10mA passing through it. Voltage should remain constant provided the load current stays below about 9.5mA.
A voltage regulator is designed to take a variable voltage in (say, 2-5v), and output a constant voltage (say, 3.3v). Now, voltage regulators are typically used to power a circuit, which means they will have a current output of a few hundred mA or more, generally speaking. In order to keep cost, size, etc down, the output tolerance on voltage regulators are (again, generally) a few 10s or 100s of mV.
For example, the RG71055 voltage regulator has a minimum output voltage of 5.2v, and a maximum of 5.8v, with a target output voltage of 5.5v, and can source 30mA. That's about a 5% voltage tolerance, assuming I number crunched correctly.
On the flip side, a voltage reference is designed to take a variable voltage, and deliver EXACTLY the rated output voltage. For example, the LT1790 can supply 5v with a tolerance of 0.1%, which is a 50x improvement over the RG71055. However, the LT1790 can only source 5mA max, which is 6x less than the RG71055. A voltage reference is used when you need to know that this line is exactly a certain voltage (in other words, really tight tolerances). On Digikey, you can get a voltage reference with 0.01% tolerance. With voltage regulators, you'd be lucky to get one with a 1% tolerance.
Best Answer
You assume correctly - you decide on the voltage regulation point (volts), subtract that from your power supply voltage and use the difference voltage and a resistor to set the operating current.
Take into account how much current flows through the other resistors too (if using them): -