If your flares check out under pressure with soapy bubbles, in my opinion, pull it under 500 micron go for it. Vacuum is rarely held for more then the 5-10 minutes needed for the gauge to stabilize. You're stabilizing at under 500 - I give that a green checkmark.
Your setup doesn't have a hose, but it does have seals based on rubber sealing against the flare service fittings. Over time, they will seep vacuum in my experience.
The only thing that gives me pause about any of your readings is the 30PSI drop over four days.