How does a DC generator vary power output to suit load
My concern is that the the motor can output significantly more current than the lights will require. I realize the load dictates the current being drawn from the generator, but if someone is pedaling hard and determined to max out the generator, will they be able to overcome to counter torque cause by the magnetic fields inside the motor and fry the lights, inverter, and/or power supply? If no, why not?


If you realize that then you already know the answer.

Rather than speaking in riddles I'll give you the answer black on white. A DC acting as a generator is not a current source. It is a voltage source. Here's the difference:



See what happens when I increase the resistance of the load. For the current source it goes bad (imagine if there was no resistor => you'd see sparks across the terminals of a DC motor), perhaps in a way you think. With a voltage source the current is lowered. To, as you were saying, dictating the current being drawn.

The DC generator can't force current into the load because it is a voltage source. Like a battery (with a very noisy output). If you can buy that your load will work with batteries, then it will work with a DC generator.

Here's some extra information for you, if you take a DC motor and short its terminals and try to rotate its shaft, then you will feel that it's harder to rotate than if the terminals wouldn't have been connected at all.

Let's take the pedaling in different angles for an example with the same gear. If you are pedaling up-hill, you are putting in much energy to push yourself forward. If you however are pedaling on a straight ground or even tilted down-hill then you will feel that you won't have to put as much energy into the pedaling. It gets much easier to pedal right? The same thing happens for the DC motor if you put a load across it vs no load at all.

Same thing happens in a car, there's a generator there as well. Let's say you're using a custom 10 W amplifier for listening on radio non-stop. Then the generator will drain 10 W mechanical power + losses. 

To quote you which is the correct answer, the load dictates the current being drawn from the generator.