You have to set inches at Options - Current Drawing Preferences - Units. Also the settings for Format (engineering, architectural, decimal..) make a difference, but I am no specialist in imperials. It seems to be right for me in this test file:arch_inch_1_96_101inches_1.dxf
You can provide a sample file here, so that I can have a look at it.
Or is it a total misunderstanding: do you think LibreCAD recalculates all lengths automatically when you change an existing drawing from mm to inches? It doesn't. You then have to scale the whole drawing with 1/25.4 or 0.03937.
I will be away from tomorrow for a week.