I need it to be feathered a bit more, like so the shadow is not just a line but has more of a fading effect into the wall
My wild guess is - rendered in blender internal, not cycles. If so, check your lights shadow properties and bump up samples. Expect rendertimes to increase :(. Some minimal compoziting at the end. On the other hand, sharp shadows, contrasts - fits to cosmic scenes imo. This blown white and sharp shadows look good. Anyhow, here’s how it would look with smooth transitions.
I’d start in complete blackness, then look at one light at a time for one effect at a time, roughly in this order: basic exposure; highlights; shadows; emphasis.
“Basic exposure” is to make sure that every part of the frame is evenly and minimally exposed. The next two lights are deltas from that basic exposure: adding light, and, yes, adding shadows. The final group of lights if any are the ones that the viewer might (or might not) specifically notice … the lighting that is “part of the scene.”
More than one rendering technology can be combined into the same basic scene.