As far as I know, you can't mold a sphere or cylinder unless the material is on the outside of the mold and you keep the mold in place. Think paper machee over balloons.
There is no way to get the balloon out. There is no way to get material to the inside of a hollow mold unless you can spin the material onto the walls, which won't work for carbon fiber.
If I understand correctly, it sounds like you want to make a short carbon fiber tube. This can be done by wrapping the carbon fiber cloth around a mandrel that has the diameter that you want the inside diameter of your tube to be. There is an excellent video that demonstrates the process. Search for “How to make a roll wrapped carbon fiber tube” on ...
Evacuating 10 psi of pressure from a 500 cu ft chamber in under a second is pretty insane. This is a good calculator, as you will probably need to change your parameters (most likely time) in order to find a suitable pump.
As you have stated, a partial vacuum in the grey water space could be causing the water level in the pressure sensing tube to rise. It’s drawing water up the tube. The actuation level is probably set for atmospheric pressure in the grey chamber.
Level Probe from Wikipedia