generally speaking, the actual chainline of most track setups is more like 42.5-43 than the mystical 42.
assuming accuracy and precision in your hub measurements, your math is kosher. however, i, like jose r, find it hard to believe that the paul track hubs would actually have that chainline.
anyhow, if you are correct, you figure that you'll need to push your chainring out somewhere between 2-3mm.... or, alternatively, that you need to bring your cog the same. that would be my recommendation -- if you currently have the flange of the cog facing outward, you can probably cut around 2-3mm by flipping your cog so that the flange is inward.
i would go ahead and buy the 109mm sugino 75 bottom bracket (or a 107mm shimano or some such) and not try to engage in any ghetto-riggery. this way, you'll always have a proper track chainline up front should you wish to switch to different wheels, put the cranks on a different bike, etc.
if the cog in the rear is already flipped around and you still have around a 45.5 chainline, then you'll probably want to go with a longer bottom bracket. just be absolutely sure that your hub measurements are accurate (i'd probably try to contact paul for the actual specs) before you go dropping cash on a bottom bracket that you'll only really be able to use on that particular setup (that is, the 75s with pauls).
hope that this makes sense.