Looks like you guys just troubleshot the rest of the way through it! :thumbup:
Yes, the momentray switch was not working with the Jeep off because we were using an ignition switched source for the trigger wire. Hooking the switch up to a constant 12V+ will fix that problem. I don't see any reason why it couldn't be the same one the + and COM terminals are hooked up to. All three have a very low amp draw.
I'm no LED pro so I'm not much help in regards to the grounding vs. in-line question. I believe if you install the LED in-line, it will reduce the amount of voltage that makes it's way to the relay. If you ground it, I think it will allow the full 12V to reach the relay. I do know for sure though that they are polarity sensitive. They need to have the correct terminals hooked up to + and - in order for them to light up. If you want the LED on only when the timer is activating the fan, then yes, connect the positive lead somewhere between the timer and the relay on the N/O wire. If you want the LED on anytime the fan is running, it will have to be attached to the fan's power wire, either the factory one or the piece you added between the new relay and fan. Depending on where you want to mount the LED (assuming it's not going to be behind the glove box with your timer), I think it would be easiest to just run the positive wire to it and then ground it near where you install it.
I'll try to draw up a final version of the wiring diagram for both Plan B and Plan C and post it to the thread for easier future reference. It's really a shame plan A didn't work as I was hoping, that would have been really slick and easy. Glad I could help you guys through it. Thanks for being patient as the plans changed!