i get really confused with how to construct over hangs and roofs lol. Is there a reason why i should make them so long?
The purpose of the overhang is to keep the weather off the vents. If you look at the native architecture of any place in the world that is subject to heavy storms you'll see deep roof overhangs protecting the walls.
Already added the windows and made the windows so i can’t make the windows any bigger. They will be top hinged windows anyway. How big should i make the vents then?
Instead of those tiny vents make big vents across the entire top of the wall and use a top-hinged cover to keep the weather out where there isn't enough overhang.
You want to think in square feet, not square inches, and, if possible, make enough upper-level venting to provide the entire 1 square foot per bird so that the windows are supplemental vents that can be closed against storms.
