The rapid cutoff at 27 to 30 psi suggests that that is the prechrage pressure of the tank.
How high is the water in the well when not pumping?
What kind of pump do you have? Submersible? Jet?
What model is the pump?
The comment about "static yield is 25" isn't a term that means anything to me. Does that mean that the water is at 25 ft from the top when not pumping?
If it is a jet pump then you cold be running out of water.
If you have a 1/2 HP 7 GPM submersible pump and the water is at 25 ft from the top you could be overloading the pump.