You do not use a microfilter on the modem - you use it on any telephone that is sharing the same line. You need a phone jack by the computer, if you have to run a pair from the kitchen up there through the walls, you can use any old telephone twisted pair cable.
The best thing to do if you want a network is get a combo ADSL modem/router, you can put that anywhere within reach of a phone jack, if it's wireless capable you can use either or both wired and wireless to connect devices. Its wired capability will be Ethernet, not USB. 802.11b/g wireless is in fact 2.4 GHz so I'm assuming that's what your TV sender is using. All you would need to do is make sure the sender and the router are on different channels.