Neither of those would be good for more than one chicken.
Yes, that's what I use too.
Details on small batch EL in this article:
https://www.backyardchickens.com/articles/aarts-extreme-weather-spiel.75893/
Ehhhh....it's kinda small and short.
How many birds are you wanting to keep?
It would need lots of work(how handy are you?) and not sure the wood is sturdy enough to do that.
Yes, big open windows, that are not protected from the weather.
Welcome to BYC! @floral_chickadee
Where in this world...