ForTheLoveOfSilkies
Free Ranging
Hello and Welcome!
You are very thorough in your post!
You could get Aristopet bird mite&lice spray in Australia or something similar to that product where you are... Active ingredient Permethrin. And spray your silkies with that and also the coop. For the flaky/dry legs you could try Vaseline as suggested or oil. I have a little spray bottle I fill up with olive oil and spray my silkies feet/legs if I see any dryness. Quick and easy. But you do have to do it consistently every day till you see results then a week later again - this suffocates the mites.
For the perch situation - how high is it? Silkies don't fly really so make sure its low enough for them to hop up onto. Some silkies do prefer to sleep in a pile together on the floor but all mine perch. They may need to be taught how to roost so just keep placing them up there at roost time and they'll get the idea.
Post some pics of your silkies and we can give you an idea if they are boys or girls. Clear pics of front and sides are especially helpful.