Since the switch is so far out of adjustment, replace it with a 30/50 due to the age and type of pump you have. Clean any debris out of the port it attaches to or any tubing or nipple it is mounted on, along with any tubing and fitting any tubing to the switch is screwed into and the holes the fitting is screwed into.
Adjust the air pressure in the tank to 29-28 psi with no water in the tank and see if your problems clear up. If not describe what is happening then.
Quality Water Associates