Converting single ended to differential signal with differential amps
Ground the 100K resistor (Pin1) in the first example, rather than connecting it to the input, to get a gain of +10.0 for the non-inverting side. 

I don't know what you mean by power it through a voltage divider. It should have a power supply of something like +10V and -10V regulated to work properly. +/-15V is what it is specified with.  

20 feet of shielded twisted pair wires will be okay, provided the capacitance of the wire does not exceed 50pF/foot, otherwise the amplifier may go unstable. You should also consider protecting the outputs of the amplifier with some hefty TVS bipolar diodes. It would be better if you could put at least 100 ohms in series with each output.