That dark part of the basement is a problem and I totally understand. It would bother me a lot too. Have you thought about buying a standing floor lamp and shining it towards the dark area and just lighting it up somewhat? I used to have a floor lamp that had all these "arms" that made directing the light easier. May help with the darkness, depends on how big that dark is.
Like this
https://www.walmart.com/ip/Your-Zone...-Lamp/21674362