To finish this up: the enviro safe website shows a chart of pressures to temperatures as a guide to refilling. I was using that as a guide. The can of freon actually says to keep the low pressure between 32 and 42 psi. I checked today, and I am at 45 psi.

In rechecking I did as suggested and let the low pressure leak onto my fingers; it seems my fluid is quite oily. So, while not scientific or even slightly methodical, I decided not to add any more oil on the basis of that test. Thanks to all who contributed! My cooling system/ac renovation is complete and everything is working like it is expected to work.

Next up: how come I don't have kickdown, anyway?