Ended up replacing the brake cable and housing with the one off Miss Mercedes. A royal pain hooking everything up with those clips and cotter pin, but think should have done it sooner. Once the prior cable was out, could feel how it was really stuck. Just don't get how it happened, but loaded up the replacement with graphite cable grease as best as could.
Ended up rounding the end of the adjuster arm with a file and patience, the one the cable pins to, as was binding on the corners. Fairly neat, but not factory. Most important, it helped.
Now have a parking brake that snaps up and engages with four clicks maximum. Nice and high like I like it. Will see once driving if needs to be slacked so the shoes are not rubbing.