I've recently been plagued with a rather annoying error in Create-a-World, in which whenever I open Edit-in-Game mode, I get a black screen. After waiting 10-20 minutes for Edit-in-World to open, my game crashes. All I really want to know is if there is any work-around. Could anyone point me in that direction?

I had the same problem. I created a separate C:\Users\name\Documents\Electronic Arts\The Sims 3
for edit in game with just the lots and stuff I needed and a separate for game.

I change my game documents name to another name such as sims 5.
Start the game and it will rebuild these documents minus any CC.
Install any lots and things you need for CAW.
When you are finished with CAW change the documents to another name such as C:\Users\Name\Documents\Electronic Arts\CAW
and rename your original game files from Sims 5 to Sims 3 and play.
When you want to use CAW just switch them out.

Under Create/create-a-world you can find lots of troubleshooting tutorials as sticky, but there is also lots of other things there.

You can use edit town too.But you must use your city's save game to play with it.