Calculating uncertainty in a current divisor
Sanity checks: -


If Rs increases by 3% then the current through the meter rises from 50 uA to 51.43 uA when 1 mA feeds the circuit
That's an error of 2.86%


OK I agree with part 1 of your answer. But part 2 seems all mixed up. Extract from question : -




You didn't alter Rs in the denominator to account for it having an uncertain value.
Putting the numbers into the formula (corrected or not) does not give 3.15% by a long way