i'm not too knowledgable about Rewire stuff...but from what i remember, you have to start-up Reason after you start-up the program that it's going to Rewire to...if i'm not mistaken, that's how you do it with all Rewire progs? start the slave prog after the primary?
anyways...about the routing problem, if you flip the rack around by hitting 'Tab' and then scroll up to the very top, you should see the output channels. usually only 1 and 2 will be used and they would be connected to your main mixer or a Mastering Suite Combinator, or anything of the like.
usually, the other ones are used with external audio interfaces for full 5.1 channels or even more if you're feeling crazy. the most i ever use is 3, two for a stereo out and the third for a separate 'click' track. the reason being, when i use Reason live, it's usually along-side a band which means the drummer would need the click...but yeah, that's a whole 'nother arena.
anyways, that top module should help you with any Rewire routing problems you're having. hope that helps! cheers an g'day.
-Ted Johnston