If you do a google search for an "AYC pump tester", you can rent a Pressure gauge for £20 from Erento, that lets you know how close to optimum the pump is still running.
If its just a little bit off on a hot day, but fine when cold, then fitting a slightly lower rated switch still keeps the system working within a working range, but if it turns out the pump is well off a useable state, then sending it off for refurbishment is probably the best option than fitting a lower rated switch.
It is safe to run without the pump running, but your just going to scrub the outer edge of the front tyres as the back end is not doing anything to help dial out the understeer.
The Evo 7-9 uses a variable sensor to monitor the internal pressure of the pump, sometimes its just the sensor that has failed, and a replacement can be bought off ebay for £99, or else a pump refurb should cure. Again using a pump tester should let you know whats wrong, (solenoid jammed, accumulator not helding full pressure charge etc),I dont think an electical code test will help as much.
Hope your problems solved by now.