I think all the confusion is coz I hijacked this thread from another op whose problem is similar but a slight different than mine. I am gonna start a new thread now. Allan sir, please check your pm. The last shared drawing is quite near to the solution I was thinking. only the 0.5Ohm shunt to be inserted anywhere in the loop.
Edit: New topic posted here Measuring Low Ohm with micro-volt resolution precisely - General Electronics - Arduino Forum