If you aren't sure if it's the pads or shoes sticking, then a bit of engineers blue on the discs (or marker pen across the braking faces, then rotate, if it rubs, the pads/calipers are sticking, if not then its gona be the shoes by elimination.
According to the Handbook, the parking brake should be 9-11 notches, so yours sounds like it's adjusted about right, could be full of solidified brake dust I guess, worth trying to blow out with an airline/brake cleaner if the adjuster doesn't seem to be working & you can't get the drum off, a few gentle taps with a persuader may not go amiss either (usual H&S disclaimers
) .If it is the pads sticking, then it could be something as simple as the sliders jammmed with crud & it just needs a good clean & a lube with a bit of copper grease. I sorted Ant & Decs at the Bash, brakes were squealing horribly, really hot, the calipers had been painted in situ, the paint had formed a wedge in the rear of the slider, crud built up & stopped the pads sliding back, quick strip down & clean, up & it was sorted.
