What sort of a half baked project is this, some junior school kiddie science project?
You tell us that you want to shut down when there is no power to the pump, but, now there is no pump!
There is a pressurised gas canister, what the hell is that! A CO2 cartridge for a soda syphon or a 30kg cylinder of propane?
In the real world where things can go with a big bang:
You dont use proportional control valves as a safety shutdown valve.
Valves fail to the safe position on power failure, so if the safe position of the valve is closed, it closes, if the safe position is open, it opens. All without external power electric, pneumatic or hydraulic.
If you want help, ask the correct questions and tell what is really there, not just half a story, most of which is wrong.
JimB