Surfing Super Center

Hello all. I live in a studio style apartment outside of my mother-in-law's house with my girlfriend. The apartment is in the back of a tool shop. When I am in their house my internet speed is up to 56 Mbps, however, when I am outside in our apartment, the speed drops dramatically to 2 sometimes 5 Mbps. We have wireless DSL and we do not have a wireless router hooked up, it is a wireless modem. However, I do have a brand new wireless ROUTER that I can hook up if that will somehow make the signal better. I don't really have the money to spend on any type of repeaters, signal boosters, etc. and the homemade antennas seem too complicated for me. Could someone break down how I could increase my speed up even just a little bit to be able to surf faster. Other details: Shop is apprx. 30 yards from house, tin roof. Here is a link to the "floorplan" of how the house and shop is layed out and where I am / the modem is ... etc.

http://i102.photobucket.com/albums/m86/WCHudgins06/Sketch.jpg