Hi,
I'm just curious about a thing.

For the story, I have a very good world with a lot of thing where I am at end game stage. It's boring having nothing more to do in Minecraft so I would like to add a good mod like this one but I'm afraid of breaking my world.

If I add this mod, will I have a problem with already loaded chunk? Can a structure or a boss spawn on my builds or around ? And can my world be corrupted?

You'll probably have to go out to new chunks for the structures from this mod to spawn. Most mods that add new structures wont mess with already generated chunks.