Just as a last late update to cap off the thread the tank is now filling up normally. I got the gas level down to about where it was when the problem first occurred and it filled up to just over 13 gallons. Possibly a faulty pump stop or a direct link to the non-seated gasket between the tank and the pump but I can't say. Anyway she's running like a top, theres no more gas smell, and the tank is filling like normal.