Will,

Have you set the units to feet? (not the length and angle) I ask as you said you set it to imperial which is a choice in the length selection.
when I import an OBJ file from Moi I get the same dimensions as long as the units are the same in moi and blender. also if you are having trouble importing FBX file download FBX converter 2013.3. It's how I get FBX files into Blender.
cheers,
Val