Unfortunately chickens don't come with a manual.

We all had to learn from our mistakes, my first coop was way too small and had the worst trouble with frost bite. They hated the coop and I had the hardest time rounding them up to get inside.
Lots of chickens fuss on the bar at night. I try to find who likes who and try and space them out before I turn the lights out. They quiet down quick in the dark.
Definitely lower your bars if you can. I have a low window too and I just don't leave it open in case predators do look inside which would definitely scare them.
You will learn as you go and make the adjustments needed. It can take years to get the perfect set up!