As far as the light being dim, that sounds a little off it should be fairly bright
though I would also check my ground connection cars hate having crappy grounds. Also it will not get any brighter when you apply the brakes, it won't do that with out special electronics (which would be costly and I have yet to see any one do it yet, although my old man explained the process that would be needed and which electronic parts I would need.)
One Question though : you said that you wired the steady-on wire to the brakes. Now was this to the wire for the brake signal or for the night lights(turn you headlights/taillights on)? IMO because the fog light doesn't brighten with brakes applied, it is better just to tie it into the night lights so that way it just comes on and stays on rather then having it come n every time you hit the brakes because it looks cheap when it lights up but is no where near as bright as the rest of the brake lights.