Still too risky. For the next time you need low pressure, turn the regulator to zero then very slowly increase the pressure until you get a slight bit of air coming out of an open hose.

The systems nylon tubing can handle much more than 30 PSI however the connections and bellows likely can't. Atmospheric pressure is ~ 14.7 PSI however the lock system can't generate a perfect vacuum so the effective pressure under vacuum will be less.

In other words when the pump is directing vacuum to the system, there is never more than say 10 PSI atmospheric pressure externally pushing on the system. In this application we can be pretty safe in assuming that if we can generate vacuum to this level we can generate pressure to this level.

I'm sure Diseasel300 will whip out his slide rule and Friden EC-132 calculator and make a fuss but we aren't trying to do something silly like send a human ( or 3 ) to the moon and back.