Here is my thoughts. Where did the water standing on gas tank come from? Could be leaking from that point past gasket into tank at sending unit or the other port in center. Next suggestion is when you take the glass tank out go get a nice new aluminum tank to go back in. Maverick/Hewes did a recall on their skiffs with glass tanks due to the glass being softened by gasoline and leaking/causing fumes/allowing water in. The fuel vapor line going to gas cap probably vents by pressure on outside edges of cap not directly through cap. Might need to replace that piece due to age. But post up the pics and problems on thehulltruth and I bet them guys get ya steered in right direction. And yes always check the Flux Capacitor!