I also tried making the input ground, and got a constant "0" and then made the input 5 volts and got constant "1023" as well,
That suggests your arduino system is working.
I measured the voltage I was getting on the analogue pin itself and it is working like it should, it varies how and when it should, but I still get the constant value of "1023" on the serial monitor.
That suggests your arduino system is not working.
It is logically inconsistent to have the two statements above true at the same time. Therefore one of these statements must be false.
There may be some loose connection or other inadvertent change in wiring between the two tests.
Thanks for posting the code and the photos, unfortunately I can't spot any errors.
I am at a bit of a loss as to what to suggest next, only repeat those tests looking at the output on the serial monitor.
When I say on the analogue pin, you do know I mean pin 23 of the 328 chip?