I've raised silkies and silkie mixes for a few years now and they are by far the most likely breed I have had to get caught by predators. Even chill predators like skunks and opossums will go after silkies. They perch low, can't run, can't fly, can't easily see without hair-cuts, and don't develop sharp nails or spurs.
They are, however, pretty hardy in the winter because of a small comb and thick feathering. As long as they are dry and away from the wind, they fair pretty well. My silkies have been in 0 F and below and been okay (adults only, young birds aren't as hardy).
They do okay in the heat too, with plenty of shade and water. They like to dust bathe in moist dirt to stay cool as well.
Silkies can be bullied, but it really depends on how they are raised, the individual flock, ect. Provide plenty of perches, nest boxes, space, barriers, and multiple feeding and watering spots and they should be okay. Keeping them separate is good as well though, as they tend to naturally hang out with each other anyways. My silkies have a mini-flock that tries to stay separate from the other breeds and rarely ever argue. In fact, I had two roosters that were friends.
Remember, mud and rain are your enemy with silkies. The chill is not the only problem, but it can cake mud on their toes and cause them to rot. They can catch a chill and get tangles. Keep them dry and trim their foot and head feathers if necessary so they can enjoy the sights of the world.
Hope this helps! Best of luck!