Thank you!
I don't seem to have tools to edit gifs, but I tried some things on a screen grab.
Here is your modified gif. As you can see, the brightest point is about 20%.
Here I've boosted that up to about 60%
Finally I used the dodge and burn tool to shape the light. (I don't know if this is possible with your tools, but doing it to just the background might work.) Note that this one has details all the way up to 100%, but still manages to look darker. Light and dark are relative - You need light to portray darkness well.
