Sons 300m and I need help please!

I know you saw 50lbs on the Schrader valve, my Pontiac did the same thing. I had the fuel filter changed on the last oil change. The place billed me for it, it was one of those quick oil change businesses. I was in a hurry. They didn't and the motor died. I thought it was the pump, bought a new one and a filter just to be safe. It was the filter! The original GM was still in it. About the same mileage as yours and same symptoms.