You will see the male collecting the fry and blowing them back into the nest when they make little dashes away from the it. Once you can see that he is constantly on the chase collecting them they are in danger of being eaten in his frustration. Then is the time to remove him.
First of all, male "ducks" are called drakes. If the female is currently laying on her eggs trying to hatch them, it should be fine to leave the male around. If she's not take away the eggs from her. Unless they are fighting the male is fine.
you decide
Eggs should be chilled before dying. Ideally you would hard boil the eggs before dying them or empty the raw egg to remove the yolk.
Yes, then clean the box.
If they froze solid then there is little point in allowing her to waste the next 21 days trying to hatch non viable eggs. If you remove the eggs she will start to lay more to replace them or go off brood altogether. If the eggs merely got cold then she may continue to brood with only some reduction in a full hatch.
sometimes with chickens any way take them away from the eggs into a new location temp. and when they have forgotton put them back and there fine unless re introducing them to the flock gets them picked on
No they wouldn't because they might or could get sick so you should throw the eggs away immediately.
Take them out of the tank and separate them. They'll most likely eat the babies.
When there are all the eggs laid, remove the male from the cage and keep him separate.
They won't eat frogs. They will probably nibble on the eggs, so it's unlikely you'll get baby frogs. You may want to remove the eggs and then put them back in when they hatch into tadpoles (they might still get eaten, but they'll have a fighting chance!).
Both male and female bettas will eat eggs, so it's a good idea to watch them closely during spawning. As each batch of eggs are released, the male, and sometimes the female as well, will gather the eggs by mouth and spit them into the nest. Once they have finished mating, you should remove the female immediately or the male will probably kill her - in nature he would drive her away, but the aquarium is too small for her to get away from him. Many males are good fathers on their first attempt, and will hover beneath the nest, picking up any eggs that fall and replacing them - leave a light on for him so that he can see the eggs as they fall from the nest. Remove him once the fry hatch. If you see him eating eggs or fry (as many inexperienced fathers will do) remove him and drop the water level in the breeding tank to one inch - once the fry are free-swimming and feeding, you can refill the tank.
whenever you want, make sure its unfertile though