Let the duck mother the chickens you will have to put the duck eggs in an incubator or under another broody duck or chicken, she will abandon the eggs.
Did your friend actually weigh the rooster because i have never heard of a 20lb cochin seems to be exaggerated.
You said it's a breed and color on your original post.
My hen turkey went broody on a few of her eggs 28 days ago but my tom died 4 weeks and 4 days before she started to go broody. So i put chicken eggs under her a week later and i just checked and seen chicks and a turkey poult. I was surprised the hen could stay fertile for over a month!
I hatch ducks i never misted the eggs before, it does take 28 days to hatch. I don't mess around with humidity, i just add water to the incubator once a week in the bottom to fill them up. Just treat them like chicken eggs and they will hatch!
That's horrible. They should know not to ship on holiday weekends especially with this warmer weather they probably too hot. Poor chicks i hope your next shipment is successful!