You can either let it out once daily, or provide a small rubber pan to bathe in.
I'm not sure at this point you can move the nest. Poultry don't understand the concept, especially this far into incubating.
You could leave stuff be for another couple of days, than block the duck in during the...
I definitely would try to block the chickens. Is the duck actively setting when the chickens let it be? You will need to separate the mom and ducklings for a few weeks for the best chance of survival.