Okay, first of all ... if you are connecting the BSD machine to the
cable modem directly, it is natural that you can not see the rest of
your local area network (assuming I understand you correctly).
What you want is to connect the BSD box to a hub (without the crossover
cable, obviously). The other computers, then, are connected to that hub
either via ethernet cable or via wireless.
Second, you are probably having issues with X because of the video card.
My suspicion is that you don't have a driver for that card, and I do not
even know if it is supported on BSD. Others on this list can probably
answer that better than myself.