Update:
Unfastening the bolt connecting the rear lower control arm and trailing arm was
as ugly as others in the archives reported. I never actually got it free from
the bushing or its nut.

I never tried a torch, but that would be my next suggestion.

I eventually drilled and cut (by hand) the outside-most control arm
bushing/bolt. Then I ground down the female bolt receptacle (it's not actually a
nut, unfortunately, or I would have snapped it off, the way I did with the strut
fork bolt) welded to the trailing arm. I used a cheap-o electric hand drill and
grinding stone attachment. Grinding it down was no fun but at least I could see
some kind of steady progress. Cobalt drill bits are essential but still very,
very slow, even with the best cutting oil.

I installed the "new" (= 8k miles used) control arm last night, attaching it
with a separate nut at the trailing arm, as I think Eric and/or others
suggested. The new strut and control arm did not fix the tilt, but I wasn't
expecting it too.

The ride seems a bit smoother, but I may have talked myself into this.

I took apart the old strut in my suspension course today, borrowing the school's
spring compressor. The shock absorber seemed in excellent shape at 157k miles
old. The spring is a tougher call.

I reckon I spent around $35 just on cutting tools for this job. About half the
tools are broken or now severely worn. I'm worn, too! :-)

I am contemplating doing the other side but not for another week or so.
Meanwhile, the other side's bolts get sprayed with PB Blaster regularly. Not
that I have much hope this will help.

Moral of the story: The classic, "If it ain't broke, don't fix it"?

I dunno. I learned a lot: -)