If they were let out when it was getting dark, they may not have had a chance to find a suitable tree to roost in and if they spent the night on the ground chances are not good that they survived. I pen mine, but will let them out to roam sometimes, but always herd them back in at night. The last time one decided she wasn't going in at night all I found the next day was a pile of feathers.
If you did not look for them right after they disappeared and it rained you most likely will never find them by looking for feathers, the rains here wash the feathers right into the ground, it is like natures cleaning system.
I know it's a little late but I still wish to give my answer.
1) I would have to say they try to do whatever they can do to survive just like others. Though they don't really adapt much but some in colder climates will get kind of fat. My peafowl I notice will start eating more but less active during the winter. Then they loose it during the spring eating not nearly as much but being really active. I know their environment can make changes on them like penned versus free range like mine. My penned male has a more uniform, full train, with lots of feathers. My wild male who depends completely on Nature his train is kind more wild, some feathers don't grow to the same length as the others, and some of his feathers are different, and his train is thin.
This is my wild Indian Blue Peacock
This is my penned Indian Blue peacock
2) Raccoons will go for eggs and chicks, sometimes and a brooding hen, skunks go for eggs, foxes, coyotes and everything bigger go for adults. My pup likes playing with my wild peacock but my dogs never hurt any of my birds but that's because we've trained them that way. They usually nest up high to try and avoid becoming a meal.
3) There are at least 225 different combinations. This includes the three subspecies of Green peafowl, Indian Blues, Indians with each color, each color with each pattern from 1 to 3 patterns each. There are more trying to be made though.
4) My peafowl eat: Meat bird crumbles 22% protein with oyster shells for Calcium, grass that is in their pen, alfalfa mine go crazy over, dry dog or cat food, rodents, and small reptiles.
5) They can. It takes more work when trying to make them friendly when older if they were feral compared to when it's a chick and they imprint on you. I've had some fun with my one hen doing shows and even being in my school year book. I just got a new White peacock that seems very friendly and I'm hoping to show him.
I showed her in the Fair as well through FFA
This is the photo of my and my horse with my peahen in my school's yearbook
6) The peahen can lay 6-8 eggs when eggs are not taken away and sometimes they can lay up to 30 when eggs are taken away.