Your numbers all seem fine, I'd be worried about dilution though if it's plumbed the way you're suggesting.
If you had a 100L tank and a 100L per hour turnover rate through your sump, that doesn't mean the entire water is going through the sump once per hour, as a good proportion will go through twice, three times, four times, etc, as it's constantly in flux of dilution.
The exact same situation is going to happen in the sump if the UV pump is taking from the return chamber and returning to the inlet chamber. So how long will it actually take before the entire volume of water has gone through the steriliser just once?
This is why UV struggles to be effective unless it's massively oversized. It'll be effective at clearing the water abit, as it'll inhibit water born zooplankton, phytoplankton, algae and bacteria, but larger things like parasites, even in their free-floating stage might never go through the steriliser.
Can it not go on the return line, so it's much more "in the loop", and you're cutting out one dilution ring?