So as it turns out...

...most of my disk problems were sorted out quite nicely by my anti-bonehead software and everything is chugging along nicely nicely, except that in sweeping out the resulting rubble I noticed a few more not critical but nuisancemaking problems which really should be cleaned up, one of these days. Which day (are you listening, Apple?) will be when the new OS comes out. This is something I almost always do anyway when a major OS upgrade comes on the scene so it's not really a big deal, although I was contemplating skipping it this time. So maybe it's a good thing, everything fell apart. Sort of a reminder that it's time to clean things up.