int potPin = 2;
...
int potPin = 3;
...
int potPin = 4;
So the final number for the potPin is A4 ?
Better name them someting like pot1Pin, pot2Pin, and pot3Pin.
Serial.print("stxHPI:(val2),(val3),(val4)"); // don't think this is even possible
I don't fully understand your story. I would first concentrate on reading the pots.
The important thing there is how many different values you want.
Example: 0 to 100% is 101 values, and -40 to +40 would be 81 values.
There are 1024 values available with a 10-bit A/D.
The map() command can reduce that to the number needed.
Leo..