Count Down to Engine Won't Start... Didn't!

[Inq]

I have a 2017 ED and it has the P203E and P204F codes. Even though the DEF fluid is at least 5 gallons, it used to register as empty. The count down to not starting started at 1500 miles. I've done all the suggestions including removing the tank and flushing it with hot, distilled water. All to no avail. In the last 200 miles, the same codes exist (erased multiple times) the DEF meter flipped to now reading pegged on full. I've read all the pertinent threads and was prepared to run a push button into the cab from the relay as found on this forum. My warning finally counted down to zero and turned to "Will Not Start, Fill DEF". I timed it to be at home and was getting the wiring out ready to do the jury-rig... and the truck keeps starting, but keeps showing the warning.

What's up with this?

BTW - I have a 2019 GDE Tune. It does not mention that it bypasses this, "Will not Start" warning, but so far I can still start it.

 

[Inq]

It did finally not start after a few more miles.

I took the plastic cover off the starter relay and added wires to the same two contact and ran that to a switch in the cabin. That way if the computer suddenly starts to recognize the level is full and start on its own, it'll still work. If not, I can hit the switch in the cabin.

A couple of questions:
(1) Is there a convenient hole somewhere in the firewall already so I can run the wires to the internal cabin switch? How have you run your wires to a switch?
(2) The trip computer gives the error chime and shows the "Will not start..." message every two minutes while driving. Is there some way to defeat this?

Besides that, I'm satisfied with the jury-rig. It beats spending $4000 to get a new DEF tank AND have the dealer overwrite my GDE tune.