In my experience, this is a problem with aluminum keyboards most people never mention or expect.
Keep in mind, I'm not an electrician or even great at electronics so some expert may point out that that this is a very bad idea.
While I have yet to do it on my 75, on the Filco I connected the usb shielding to the case so it acts as a ground. I can still get zapped, but it least it goes down the cable to the computer case and grounds rather than jumping to the internal electronics.
Remember, it follows the path of least resistance to ground, if your case is not grounded, it has high resistance and if that spark is strong enough it can jump from the case (or your finger) to the PCB trying to find a ground. The bad side of this is if there is lightening strike you have a slightly higher risk of getting zapped that way, but while I have seen several system hit by lightening and power spikes, none has ever left the computer tower and rarely gets past the power supply if you have an adequate power strip.
If you do this, you will need to sand through the anodizing as that acts as an insulator, and while the spark can easily make that jump, it creates a high resistance point, so if there is a path with less, it will choose that instead.
As for your current pcb, are all the leds dead, or just some. If you apply power to one of the burnt ones (from a working one), does it come on (it may be dim but should come on)? If they fail to come on with rerouted power, it's likely just the led that has been damaged. If they do come on then you have larger problems. A burnt trace, damaged controller or scrambled firmware. Odds of it being firmware though is pretty slim in my opinion simply because what are the odds it scrambled only the code for those leds while leaving everything else intact.