A couple of points:
1. The pressure relief valve is illustrated in the pressure refuel ref AMM 28-21-00 or storage ref AMM 28-10-00.
"An open pressure relief valve is a symptom of a blocked vent scoop or flame arrestor.
The pressure relief valve can also open to relieve air or fuel pressure if there is too much pressure during refueling."
2. Float valves in the vent system block the vents from filling with fuel as the fuel level increases and drain the vent channels of fuel that gets in there.
The only air getting in the tank is from the vent system and this is normal.
3. The jettison manifold is connected to the eng feed manifold thru the jettison manifold isolation valves. It is not open to the tank itself. The main tank jettison pumps feed the jettison manifold itself and the center tank override/jettison pumps feed the jettison manifold through the engine feed manifold through the isolation valves and into the jettison manifold.