If you are running a locked timing motor and trying to keep up with others that aren't, you are going to have a bad time.

The '6 amp setting' is an okay baseline, but that is just an estimate to get the most power out of the motor. It for sure isn't the most efficient way to run. If you are using the amperage method to set timing, I wouldn't jump right to 6 off the bat. Try setting the timing for 4-5 amps and running a couple full practice races that way. That last 2% of power you gain by adding more timing adds a disproportionate amount of heat to the motor.

While a fan is a great way to keep it cool, surface area plays a big factor. Add a simple clip on heatsink that the fan can blow air through to really maximize the cooling power.

Another way to make the car more efficient is to reduce toe. I know it will take some other adjustments to compensate, but 3 degrees of rear toe in a 4wd vehicle with a 17.5 motor is overkill. Going to 2.5 or 2 will reduce rolling resistance and give you more steering as well. Try to keep the front close to 0 as well.