No, that is not normal. Examine her thoroughly for any other signs of illness - things like a full crop that doesn't empty in the morning, swollen abdomen, abnormal droppings, droopy tail, discharge from nose, eyes, vent, sneezing, lack of appetite, mites/lice. Separating her into a dog crate...
I agree that introducing the Silkie will be more difficult. I had very few problems introducing my Muscovy to my chickens. Muscovy are bossy birds (at least mine are) and the chickens learn to leave the Muscovy alone, but as long as the Muscovy are left alone they don't bother the chickens...
No heat needed. Chickens have built-in down jackets. All you need to do is make sure those down jackets don't get wet or ruffled. Most chicken breeds will need heat at around -20°F.
I'm sorry! That is concerning. I suspect the deaths are connected somehow and the wounds on the other two were caused by the other chickens pecking them after they died.
Have you checked them all for mites/lice? Do they have access to anything poisonous (berries, compost, etc)?
I'd cut out...
A few things have been keeping me from rehoming them - 1) it will stress them out, 2) they could torment someone else's flock, and 3) my flock is infected with MG. I could butcher them, but that is hard because they are pets. This is why I've been trying to make it work for two years now. I...
Thanks, @Crazy Maizie. I don't have a secure run for them, just a pasture, but I don't think it would matter anyway. Even though they hurt each other they seem to want to stay with each other. It does seem like it's just a habit and there is no rhyme or reason for their bullying. One month...
My coop is not big enough for a drake, but I guess I could try to make room somehow. But even if I did I'd be afraid he would stress them out even more. I'd really like to hear from someone who has introduced a drake. @Crazy Maizie