If you have a fuse box, I would suggest you get an electrician. Fuse boxes are old, and the wiring sounds like it was done at different times, so no telling what you will be messing with.
Me and my father use to tear down houses. We got into one, cut off all electricity, and still found a live wire, the guy had snuck out to the pole and wired it direct up, we didnt' know til my dad almost died, the guy was stealing electricity for his cooking units. That was one of the most scared times in my whole experience of dismantling houses for thier lumber.
You should be able to get electricians to look it over and give an estimate free. See if you can be there when he is there, so he can tell you what to expect.
You could take the cover of the out let off, and just look inside to see if you see that flash of copper with a flashlight, do not put anything in there to move the wires around though.