resistance for input on arduino

Hi guys,
I have a problem with arduino mega ,
I want to measure the consumption of this circuit and I want to measure the resistance to find the watts
according to the formula W=V^2/R…

For example, when I press a switch not to see consumption 0 watts else if I press all the switches together
to see consumption 100mW…

I reached a point with this example >>><<<< but not potentiometer
I want to have the buttons.

with analogRead() function that read values ??from 0-1023 expect when I press a button to reduce the values but
because the circuit has little resistance does not decrease much, going from 1023 to 1022 with all switches closed,
so I can not measure watts with the scale

for example, when I press one button to decrease from 1023 to 1000.
when I press two button to decrease from 1000 to 980.
when I press three button to decrease from 980 to 950 etc…
I do not care about the exact I just want to reduce the values when I press buttons

How to fix it;
Is there a function that will help me;
You know another way (again with resistance, not current sensor)
Tell me something!!!

Thanks guys and sorry for my bad english.

4x 200 Ohm
1x 7 Kohm (9v decrese to 5-- for input to arduino

Don't do it man. If your MEGA has teeth they'd be biting your hand right now. You have fed 9V to your MEGA where you should feed up to 5V. Stop!!!

Also the resistors for the LEDs are too small.