I think it looks pretty good man. Nicely done.
I do agree on the asphalt, would probably be better to get a nice even baseline exposure of it and the layer in the lit vehicle to give it a more natural look.
With regards to running the light off of your vegabond.. I would be cautious to do that often, from what I remember in my years of owning the original and then mini, they say not to run a constant power draw source through that battery, like on the alien bee strobes it had you disable the tracking light which turned on a lightbulb to simulate the flash exposure, just a thought.