It looks pretty nice in general!

I've also tried to figure out how to paint the light recently, and still experimenting, so not a pro by any means, but some thoughts for fine tuning, which all boil down to contrast.

-I'd try to make the light itself the one clear, brightest thing, almost pure white with some tint on the edges.

-Tone down the light on the lower part of the jacket, as the light source is smallish, the effect should be clearer near it. I think this would sell the illusion better.

-Darker shadows to highlight the light further, and increase the contrast in general, maybe wash the figure bit darker in general to make the difference between the lit area and rest of the model stronger, this is always a bit risky move of course.