Any plumber/home repair practitioners out there wanna tackle one?

Go down to your local Home Depot or Lowe’s plumbing department and describe the problem to them. They will hook you up with the proper parts and describe how to install it. If you bat your eyes just right, they might even volunteer to do it for you after their shift is over.

My brother the carpenter had the same problem in his toilet. He replaced everything and just determined it was air in the lines. I don’t know if that is carpenter speak for “I really have no idea”, but there you have it.

The flapper or the seat for the flapper are most likely leaking. That lowers the tank level and makes it keep refiling itself.

There are 2 or 3 thing going on here. The flapper is leaking. They get warped if you put chlorine bases toilet bowl cleaner tablets in the tank. Stop using them. You do not need blue water in the toilet. You can replace it for $5 and 5 minutes.
Now about the squeaking sound. It is possible the valve is corroded or dirty. Take off the tank cover. See that screw on top of the valve? It’s where the float arm pivots. Turn it down about one turn. Flush the toilet and make sure the water shuts off at the right level. There is level a mark inscribed on the back surface inside the tank. If the water is set too high it runs forever. Too low and you don’t get a good flush.
The float might also be waterlogged. Look at it and make sure it floats.