My most important criteria in positioning a coop and run has nothing to do with the sun. Put it where it will stay dry. A wet coop and run is a danger from a disease standpoint and can easily stink. Do not put it in a low spot where water collects. Put it where water drains away.
Heat kills a lot more chickens that cold further north than Pennsylvania. With just a little bit of help they can handle cold really well. They do not need additional heat any more than the songbirds that overwinter in Pennsylvania. They need good ventilation like songbirds get when roosting in trees but they also need protection from direct wind blowing on them. Songbirds can get that by moving out of the wind but we usually don’t give our chickens that much freedom in the coop. Openings up over their heads when they are on the roosts will give them good ventilation and prevent direct winds hitting them.
We all have our own personal preferences on a lot of this stuff. I like a darker coop, I think my chickens are calmer if the coop is a bit darker. My one window is on the north. But some people prefer a brighter coop. Plenty of people have very bright coops and do fine. Put the windows where you wish. You will be OK. But don’t worry about adding heat, it’s not necessary.
How fast and how thoroughly chickens destroy vegetation in a run depends on the chicken density as well as the growing season and your climate. If you only had that smaller run area it would not be long before it is bare dirt. With that larger area and only six chickens it could last quite a while in the good part of the growing season. They may eventually wipe it clean, they may not. As a minimum they will keep certain areas cleared out, where they sunbathe and maybe in the shade where they will probably spend most of their time.
One way to assure them of at least some forage in the good weather months is to make a grass bed in the run. Make a frame out of 2x6’s or 2x8’s on edge. Maybe two feet wide and as long as you wish. Cover that with some type of wire they can’t get their heads through, chicken wire works. With the roost well established they will pluck off small bits of green that they can reach without eating the grass to the roots, then scratching the roots up and eating them.
