Abnormal Voltage drop reading, 4 wire vs 3 wire, Singled ended input
I would not call the second one "three wire" because that name is used for other purposes. 

Your circuits do not appear to do anything useful- at best they will output some weighted sum of the voltages at the ends of the switch. 

What I think you need is the difference between the two sense wires, precisely canceling out the common mode voltage introduced by the 100mA through the force wires (and any variations thereof). 

This can be accomplished with a differential amplifier, which is easy because your source impedances are very low so a single op-amp and four resistors will work. You can also get some gain so the ADC input will be less critical. However I suggest using a better op-amp than the LM358- it has a relatively high Vos spec. A single-supply precision op-amp would be much better. LT1006 is one, but there are others.