Trying to save mallard eggs, incubation help!

[Cla55y]

My daughter and I have been visiting a wild mallard nest near our house for a few weeks to check her progress. Today we arrived to a slew of feathers and abandoned eggs. It was clear the he'd had been killed. I collected the remaining eggs and took them home to candle and incubate thinking that at least they have a fighting chance with me.
There is one definitely alive, and two that look viable after candling and the float test. My questions are as follows:
1. How will I know when to begin lockdown since I'm unsure of exact incubation period by the hen? I can estimate at least 3 full weeks by this Friday.
2. What are the ideal settings for my incubator given the unknowns, and should I be turning?
3. Should I be candling daily to check progress?
4. I definitely saw movement in one egg, but given the unknown time between when the hen was killed and I rescued the eggs, what should I be looking for going forward to determine if they are continuing to develop?
5. Anything else I should know/ watch for?
I will add that I am using a homemade styrofoam cooler incubator and have successfully hatched chicks and one duckling in it. It's not the best setup, but it's what I have currently. Humidity is regulated by adding wet paper towels and temp is regulated on a slider.

 

[sylviethecochin]

@Hatchi Wan Kenobi is probably the best help you can ask for.

I have never incubated duck eggs and know only that they require a slightly higher humidity than chicken eggs do.

 

[Pyxis]

@Hatchi Wan Kenobi is probably the best help you can ask for.

I have never incubated duck eggs and know only that they require a slightly higher humidity than chicken eggs do.

That is the best way I've ever been tagged, lol.

Pardon any typos; I'm typing this one-handed and snuggling an emu in my other arm.

Just to start with and get it out of the way so you're making an informed choice: it's illegal for you to have taken the eggs, it's illegal for you to hatch them, and it's illegal to keep the ducklings after they hatch. Mallards are covered by the Migratory Bird Act. Taking the eggs and hatching them violates the law and penalties range from large fines to jail time.

Now, there are domestic mallards, but they are marked at hatch in such a way that if anyone checks, there's proof that they are domestic. Is anyone ever going to check yours? Probably not, but it's best to be aware of what could happen, however unlikely.

All that said, on to your questions. Temperature at 99.5, humidity around 40% for now. To see how far along they are, I would compare them to this candling chart:

http://www.metzerfarms.com/Candling.cfm

Candling daily isn't necessary but won't hurt. Look to make sure the veins aren't disintegrating to make sure they're still alive. You should also be able to see movement.