Electric fuel pump failure. Recommendation?

Never, ever use a returnless regulator on an electric pump that was not specifically designed for it. Otherwise you get the pump's maximum pressure between the pump and the regulator. A return type regulator lets the pump's output pressure drop to almost the same as the carb's. The other options are to use a pump with a regulator inside the tank or an electronic pump control that slows down the pump to match the pressure.