Design Assumption.
When incoming current equals to outgoing current through sensing resistor, or difference between them equals to nearly zero, no leakage is happening in the circuit.
No. If incoming current equals to outgoing current through sensing resistor then all you are proving is that there is no leakage to earth from the resistor. It doesn't tell you anything about where the current goes after that.
All your circuit can do (if you remove all the other design problems) is measure the current through RSENSE.

Figure 1. Points at which to monitor current for earth leakage.
If you really want to check for leakage you would need to measure the difference between the current at (1) and (2). You might be able to do this by using running two conductors through a Hall-effect current transducer so that the two currents normally cancel out.
Others have already pointed out some of the other problems with the circuit.

Figure 2. OP's version 2.
In principle, this idea would work but note that you have not got the circuitry to work out the difference between the two current sense amplifiers and this will have to work whether the error is positive or negative.
The big problem with this approach will be with the precision matching of the high and low-side shunts and amplifier resistors. This will be even more difficult if your power-supply voltage is higher than the op-amp and ADC maximum voltage.
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