[P-hack]

just for fun here is my attempt at a working program, no ownership implied

int val = 0; 
unsigned long time;
boolean overboost;
void setup(){
  pinMode(0, OUTPUT);//don't need to set pin 3 for analogRead
}
void loop() {
  overboost=false;
  val=analogRead(3);  //
  //val should be between 204 and 716, 1v and 3.5v
  val=val-204;//  val between 0 and 512 
  if(val<0) val=0;
  if(val>510){
    val=510;
    overboost=true;
  }
  val=val/10; //val between 0 and 51, just right for 1v pwm
  if(overboost){
    time=millis()%500;
    if(time<250){
      val=0; //turn off pwm for 250ms out of 500ms 
             //  so the display flashes indicating overboost condition
    }  
  }
  analogWrite(0,val);
}

Binary sketch size: 1,460 bytes