rust;
In asking about PWM and Amps, you seem to indicate you want to vary a voltage for a HEAVY load.
The PWM outputs on the RC give little pulses every so often, NOT a continuous steady voltage. I haven't checked the timing since the 98 season, but they give an approx 1 ms pulse every, perhaps, 26 ms.
The way to achieve your end is to use a translator that will handle the current, and take the PWM signal and turn it into a voltage level. One such device is currently available to you : it comes from a company called Innovation First, in Texas. It is called a Victor 884.
It gives square waves with a duty cycle from near zero to 100 % (not a square wave, just continuous 12 V). If your load can take 12 V with an average viltage of your choice (for instance a lamp, but not a portable radar-on-a-chip with a requirement for filtered 5 V dc)) then this is the way to do it. Current reportedly up to 40 amps.
Connect it, and in your program, limit the pwm signal to the maximum you want, and don't go to the other side of 127, if your load is polarity-sensitive.