Sorry for the wall of text in advance, I think a lot of your questions have already been answered but here is my experience with silkies in case it is helpful.
I am getting into breeding silkies and I love them. Most of my girls are very docile, a lot of them like coming right up to me and are very easy to pick up and handle (sometimes they can be a little skittish when young but usually get a lot friendlier when they start laying). I've had bad luck with silkie roosters being aggressive, I've got some cockerels right now I am hopeful about though.
I've had silkies in mixed flocks in the past and never had any problems with them being picked on or picking on others. In my mixed flocks they tended to be a little more reserved, but still very docile and easy to handle.
Mine do tend to go broody fairly often, when they aren't brooding they have been very good layers and have actually been one of my best winter layers. I've never let any of mine hatch eggs so I can't comment on their mothering/incubating ability. The ones I have that go broody are very diligent about staying on the nest however and stay there past 21 days (I've got a little broody right now that I really need to try to break as she's been brooding for nearly 4 weeks now with no signs of stopping).
I have mine in a run with netting over the top to protect from hawks so I also can't comment on their free ranging ability. I do sometimes have to trim their crests so they can see better. When I had the silkies in the mixed flocks they weren't able to reach the roost that was over a foot up and slept on the coop floor instead.
As SoftSilkie mentioned there feathers aren't waterproof so they do get pretty soaked in the rain. My girls are very bad about standing out in the rain. When it rains a lot I shut them in their coop so they don't get so wet. With all their fluff heat can definitely be hard on them, I've found them to be relatively cold tolerant as long as they stay dry (though I've always provided heat for all my chickens when it gets very cold).
I have noticed more health issues with my silkies than with any other breeds I've had. Wry neck due to vitamin deficiencies or sometimes head injuries if they have a vaulted skull is something to look out for. I add poultry vitamins to my silkies water at least every two weeks to help prevent wry neck, the few silkies I had in my mixed flock didn't get extra vitamins and never had issues though.
I ordered some splash silkie chicks from Cackle several years ago (we rehomed as we moved across country and didn't have a place set up for them). For hatchery silkies I was very impressed with how they looked when they matured (nice and fluffy with decent sized crests). All the chicks survived shipping, we lost one on the second day due to coccidia I believe (it had bloody stools) we treated with Corid and though that chick was too far gone none of the others came down with symptoms. A couple of the chicks arrived with curled toes that needed to be corrected with band aid boots (the toes never completely straightened but did get a lot better). We had one chick that had issues with passing stools for several days (nothing blocking the vent) she went on to develop wry neck later on (which we were able to successfully treat) but she continued to have various issues pop up until she passed suddenly one night at a little over a year old. None of the others we kept from cackle had issues, I think we just had bad luck with the one. My cackle silkies did tend to go broody just as much as the silkies I've got from breeders so hopefully they will be a good fit in that area. I didn't end up keeping any roosters so not sure how the boys from cackle are temperament wise.
Here are some pictures of three of the splash pullets from cackle at around 4-5 months old I believe.
