Time to rebuild?

Another note: lately the idle has been really rough when cold, but fine when warm. Previously the idle was pretty smooth all the time. Today I repeated the vacuum check while the engine was not yet warm, and I noticed that the idle improved dramatically when I opened up the vacuum line from the intake manifold. Does this suggest that the choke is not coming off the way it should?

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Probably it doesn't suggest that. but I suppose it might, Easy enough to prove; just pop the air filter house off an look.
What it suggests to me is that the carb is rich. There are many reasons for that, the choke being way down on the list.
Your vacuum results seem to indicate that the rings are fine.
Your vacuum break may not be sufficient.
I'd like to see a retest of the crankcase pressure, but with either.
A) the cooling fan disabled, and the PCV removed from the cover and the hole plugged, or
B) plug all openings into the crankcase and put a pressure gauge on the dipstick tube. Use a fuelpump pressure tester. Start her up and let her idle.If the pressure builds to 4 psi, shut her down.! There is indeed something wrong, probably with your rings.Or maybe just maybe, with a headgasket.
C) Remember back in post #12; the compression test showed a 5 psi drop on cylinders #1 and #2? You might want to repeat the compression test, having made sure the valves are all adjusted the same. I would do this retest inside at any comfortable room temperature, or if you have a block heater, still inside, plug it in. Let the car acclimate for at least 4 to 8 hours hours prior to the test, depending on the temp of it's prior environment.The purpose of this acclimation is to make sure the temp of the engine does not change during the test. The actual temp of the test is less important than that it remain unchanged. Your Italian tune-up may have changed things, as in cleaned out all the carbon.The valves may have been hung open on the previous test by that carbon. Or the rings in those two low ones may have been stuck. In any case test them all.It's not the absolute numbers that will tell the whole story, but rather the differences from hi to lo.