if you set your map meshes FX to zero instead of 1 (fullbright) then it should work noless. AFAIK you cannot override the FX setting after loading, so you need to set it in world studio. But the flashlight should then be the only light in the scene. and of course in lightmap-lit places the flaslite won't be very effective, like IRL.
But don't expect any shadows with DX-lights (CreateLight).
But don't expect any shadows with DX-lights (CreateLight).