I've used 0.05 IWC for dozens of years, as my main client was DoD biological safety and agent hood use. The 0.05 IWC is exactly spelled out in the DoD standards. Because leakiness standards are leaky, I've always relied on differential volume flow and availability of a Dwyer and damper for manual set or a photohelic for full control operation. The 0.05 IWG has worked well for setting high and low limits; typical would be to set a fast acting barometric damper on supply to avoid overpressure at about 0.02 IWC and 0.07 IWC as upper limt on VFD. Door open and close will make the control swing back and forth between 0.02-0.07 IWC in my expereince using air control valves and photohelics.
I wouldn't trust calculations as much as having a balancing damper and flow control. I've seen differential flows from anywhere between 60 CFM and up to 200 CFM depending on the leakiness. If you are on the high end, it might be time to get the silicon caulk out. Specifying good door hardware is important. The Phoenix valve web site may still have good tutorials for this.
No need to maintain 0.05 IWC under open door scenario, as long as positive volumetric flow is verified (smoke the door). If contaminants or viral/bacterial agent could swim against the flow, it would be a moot point.