Hi,
the idea of the shunt selection is to have a fixed 1mA/LSB of the actual ADC reading. We call this formating of the output value.
The ADC itself does always operate the same independent of the formating.
I suggest to use the standard configuration of 100uOhm, which has a 0.1uV/LSB result.
You shunt provides 70uV/A which would be 700LSB /A or ~1.43 mA/LSB.
Rgds
W.