That actually shouldn't be too hard. Just get a bunch of stone (wood, dirt...), and start placing them in a straight line, using the sorta glitch thingy that lets you walk over the edge a bit and place another one under yourself. Soon, you have a straight line going anywhere at any height over anything. Apply tracks.
As for the sky fort, you can just build a stairwell as high as you want, then build your fort, and deconstruct the stairwell. Simple.