This time, I'm trying with the basic data for the system apps, plus HandyShop and Bubblet. If that works okay, I'll add parenslite and then see if I can dig out new (and presumably more trustworthy) versions of DateBk4 and MetrO. MetrO updates frequently, so that shouldn't be a problem. (I don't know it's corrupt, just playing it safe because it comes with a lot of files.)
Adding just Parens_Lite.prc got me a partial program with stuff grayed out; I'm guessing that the necessary files are mathlib.prc and libmal.prc, and restoring them. (Yes, that's right--and it's still cool.)
Re-downloaded and installed DateBk4, so far so good.
20:10 And now the digitization has slid off, and the "prefs" screen--which is where I would go to fix that, and to set the date and a variety of other things--doesn't take input, though bubblet and calc do. I think MetrO is presumptively not guilty, and I may try again without bubblet--much as I like it, I don't actually need it.
10/8: Tried again last night, with bubblet but not DateBk4. Am now adding MetrO, and we'll see.