You have a proportional inertia brake controller. When the controller is set up correctly you will not and should not feel the trailer braking the TV. It should feel more like there is no trailer and brakes much like if there was not a trailer attached.
A wiring upgrade most likely will not help anything if you are seeing only 20-30% on the display with heavy braking. The controller will increase the voltage to the trailer brakes until the accelerometer sees a decrease in acceleration. Thus if the controller reading is less than 90 % then it is able to supply all the voltage and current needed as seen by the accelerometer.
If you have the controller setting to high it can get you in trouble during a stand on the brakes situation. The trailer brakes may lock and you may then find the trailer leading the way to the accident or turn the whole system on its side as you skid on you side or upside down to the accident.
