This has happened to me before but I was able to make it home.
This is what I think: At the two large terminals on the controller relay: One is where that bent flat bar resister is connected. That is the secondary side of the relay where the current travels from the relay through that resister to the glow plugs. DISCONNECT THAT SIDE at the large terminal on the relay and move that resister out of the way. There is a bolt that holds it down at the bottom end which connects it to the glow plug harness and you'll need to loosen that bolt to move the resister to the side, or you can just take the resister out of the circuit and reinstall the bottom bolt. Now the glow plugs and that resistor are disconnected and out of the circuit.
When a GP controller relay sticks closed that resister will consume a huge amount of current and get extremely hot! Hot enough to melt through the plastic cover that goes over the top if you still have the cover. The hotter it gets, the more resistance it has and the more current it consumes from the batteries. That will drain your batteries faster than the glow plugs. IT WILL ALSO PROTECT THE GLOW PLUGS FROM BURNING OUT.
The other side of the GP relay is the primary side which is connected to Battery voltage. I THINK (I'm not certain) that side needs to stay connected for the ignition key starting circuit to work.
Otherwise, if that side is disconnected you can probably tun the key on and jump start it across the terminals of the starter relay on the fender well (If that's where your starter relay is located)
I've never been able to start my truck with the ignition key after disconnecting the power supply wires that go to the primary side of the GP relay, by disconnecting them at the starter relay. That's why I THINK that the GP controller relay needs power to the primary side so truck will start with the ignition key.
LAST, from memory only, I think there is a small wire with a ring terminal connected to the secondary side of the GP relay. It's from the controller. I think it's white? I don't know if that wire needs to be connected to the secondary terminal or not for the truck to start with the key , but what I described disconnects the major load of the glow plugs and that resistor from the circuit so it won't kill your batteries.
Later today I'll post some photos and the story of my experience with this. I cut open the relay as part of the diagnosis so you'll be able to see he insides of one burnt relay
HEY, it could have been the controller that failed and caused the issue.