I would get the salt right first and then see if the salinity is correct on both polarities.
Get a k-1766 salt test because it is the best test.
K-1766 Taylor Salt Test
I suspect that, based on the age and different salinity readings on different polarities, that you will probably need a new cell but let's confirm first.
So should I buy shock?
Or liquid chlorine ?
I added a 40 pound bag today