We have both pullets and roosters that get roughed up very bad sometimes and I have to hold them while my wife the nurse cleans their wounds and applies antibiotic ointment. Sometimes they are in shock and it is easy. Other times it is very difficult to hold them still so when can see what she...
I doubt that they will ever coexist in the same pen no matter how big or how many hens are in it. For the peace to be kept most I don't see any way except for separate pens for east set of them. Below freezing shouldn't be a problem as long as you have sufficient wind breaks and rain...