Isn't it possible to use water from the Black Sea (and thus the oceans) to flood the Caspian Depression and thus make the Caspian even bigger?
With regards to the Dam of Darkness, considering its iconic status would that not make it a target of anticolonial terrorism?
It would certainly be a target for anticolonial forces to seize, regardless of what they do with it?
Does it come under multinational control? Perhaps spurring an early League of Nations and subsequent Mandates.
The Three Gorges Dam can allegedly survive tactical nuclear weapons. Even given the age of the Congo Dam (Dam of Darkness, I love that name) and likely shoddy construction, it could probably survive anything smaller than a 9/11 style attack. That said, the sheer destructive potential if the dam fails means it would be a resource sink over the decades as people try to improve and strengthen its foundations and protect it from terrorism.
It's more likely anticolonialist terrorism (or for the Congo, anti-government forces and such) would just seize the place and use it to turn off every light in Africa (and possibly some in Europe if they manage to hook the thing up to Europe's power grid, which why not?).
The Reunite Earth & Moon Project: cover Moon with solar panels and arc thrusters, to slow it down so it drifts out past the Hill Radius and into a separate (Earth-crossing) orbit.
It would also make a very nice ring around the Earth once the thing impacts.