Americana (EE with traits similar to Ameraucana)do not fly any more than other chickens. There is no standard, so traits and personalities may vary more than breeds with standards.
The simple answer is yes they can still hatch. How long have there been twelve eggs? How many days has she been sitting part time? Many ducks when they first go broody don't sit 23 hours a day, but later become more committed.
It will not develop angel wing due to feeding 20% protein. I don't know about Muzuri's starter as far as other details. The feed I use is designed for all stages of life.
My eyes aren't great and sometimes miss pointed saddles in pics, but I would think the pointed feathers would be becoming obvious, and crowing regularly in 20+ week old males
My breed guess is Leghorn over Marans. Could be another red bird in the mix. With that mix I believe these could be...
Try to get your lone little one in site of the older ones. The more it is with them the easier it will be for it to become part of the flock later.
As you know ducklings grow quickly. I would actually start putting them together in the next week or so. The integration will be smoother if the...
Ducklings are sometimes as uniquely colored as adult ducks. Being they are from a farm their is a possibility of mixed breeds. In ducks mixed breeds may mimic other breeds.
If you can get a picture of them standing it may help.
My first thoughts are a Pekin and a dark Welsh Harlequin.