"I fear I may have overlooked a brake fluid change - any chance new fluid/thorough flush will restore caliper performance?"
If the caliper is sticking, the reason should be determined before continuing. The parts involved in a rebuild are cheap - piston seals and dust boots - but labor may cost more than a replacement caliper.
Absolutely the fluid should be flushed, but pay attention to its condition. If it caused deterioration of the piston seal, more problems may yet develop. But, if the dust boot ruptured, allowing contaminants to score the caliper bore, simply replacing that caliper will take care of your problems.