You're not screwed. Just use the 12awg wire that we mentioned and you'll be good to go...
I would suggest getting rid of a push trailer, it's an INEFFICIENT way of propelling the bicycle.
Get one of those Harbor Frieght motors and attached it to a seperate chain to the Wheel/Sprocket.
Buy a back bicycle rack and put a battery box on it and just run 12awg wire from the battery to the meter and then to the motor.
You'll get the best of both worlds... Effeciency and good connections.
