Pump speed has almost nothing to do with chlorine production as long as the minimum flow rate requirements are met. If 8 hours is enough for your old pump, 8 hours should be enough for your new pump. But the vendor's schedule is a little overkill in my book. 1-2 hours at 2500 and 7-6 hours at 1000 RPM should be enough run time (8 hour total). Most VS pumps have peak efficiency around 1000 RPM so I would target most of the run time around that.