Item 3 does exist, but Zwift’s home page is not the best place to look for it, Zwift Insider has a complete list of all routes, with links to maps and elevation profiles for them
I’m not sure why but this was their design choice. There have been some previous suggestions like this, like this one.
This one they have spoken about. They want to pack people onto a limited number of worlds and routes so you see more people. That is a design goal. People who don’t care about the social element are not the primary user they have in mind for the game.
Aside from Zwift Insider as was mentioned, I also recommend zwiftmap.com
Not sure if this has been proposed before but you could create a new topic in Feature Requests for it. I doubt it would get much attention but it’s up to you. There are lots of reasonable ideas about how to improve the game that are never implemented unless there is very big demand, and even then sometimes they say no or don’t say anything.
Average power in Watts is available in the HUD settings. Average W/kg or speed are not. The available options are documented here:
There are also some 3rd party tools you could use such as sauce4zwift, or a cycling computer.
By the way your point 4 might also be satisfied by having a lap button that you could press at the end of a specific performance. There is significant demand for that feature. If you like that idea, click the Vote link at the top of that topic and leave a comment there expressing your support: