Arduino CapacitiveSensor Liquid Level Mapping: 1V-5V Output, 51-255 Range Calibration

hello.

here is another liquid level sensor.  I am using the CapacitiveSensor  library.  I am making a test system with a wire inside a steel tube.  The tube is grounding via the Arduino and the wire is used for the sensor value which is attached to an analog pin .  I get a reading when empty about 4000 and when full about 7000.  I noticed that the actual pin value is 360 empty and 410 full. (these values are approximated)

- The sensor value is very touchy how could I fine tune this input?

- Eventually I will control a ball valve  by mapping the input to a PWM pin.

I am just trying to serial print the output value
I want the empty level to be 51 and the max level to be 255  is this possible?  So the output would be 1 V to 5 V . Any values outside of these would not be desired

I have tried to calibrate and capture the Min and Max values when a button was pressed but this has failed.

here is one of the codes I have written .  
Any help with this would be great
Thanks

*********************************************
/*
A 1M ohm resistor is between pins A0 and D12
a 100 pF Cap is connected between A0 and Ground
the input is to pin A0
output is from D3 to a led with a 220 ohm resister in series

*/

#include <CapacitiveSensor.h>

int count = 0 ;
int x = 0;
CapacitiveSensor   liquidLevel = CapacitiveSensor(12,A0);   

void setup()               
{
   Serial.begin(9600);
 
}

void loop()                     
{
  const int analogInPin = A0;  // Analog input pin that the potentiometer is attached to
  const int analogOutPin = 3; // Analog output pin that the LED is attached to

  int sensorValue = 0;
  int outputValue = 0;
 
   count++ ;
   long total =  liquidLevel.capacitiveSensorRaw(50);  

   
   // read the analog in value:
   sensorValue = analogRead(analogInPin);
   // map it to the range of the analog out:
   outputValue = map(sensorValue, 0, 1023, 0, 255);
   // change the analog out value:
   analogWrite(analogOutPin, outputValue);

   Serial.print(total) ;
   Serial.print ("t");
   Serial.print(outputValue);
   Serial.print ("t");
   Serial.print(sensorValue);
   Serial.print ("n");


    
   delay(250) ;
}