I can not connect to the internet?

i have windows xp pro my ip is 192.1680,2 My wireless adapter is Wireless-N 150 USB Adapter WNA1000 Now my nephew who lives a apt ment down and up a floor and he has windows xp pro he pays cox cable for his internet which he has to use a cox cable modem in order to get the internet. He also has a D Link wireless router that he has a security block on so you got to have his pass word and I do. I do everything to connect my computer and the result is I get told I have limited connectivity or I can get as far as I connect to the router but nothing from there. Now I pull I great signal shows 80% plus with 150-300 mbps. I also pull a wireless connection from a jimmy timmy cause he has a none for security but that is I get a 30-35% signal and 11.0 12.0 mbps on a good day. needless to say I use it cause its all i can connect threw. I also have a pass code from a friend with a WIRE wireless router and I can not get passed the router why is this? If I can talk my manager into allowing me to run a ether net cable from my apt to my nephews would that be better and just go off his cable modem. Is that possible to run a ether net cable about 150 yards?.