Very interesting project for a beginner!
An Ammeter with 7 digits resolution, made at home!
Using as a reference an instrument having an accuracy of 100 uV in the lowest range, while the requested resolution is 1 uV (accuracy?)!
How the amplifier will output 5V with 1.65V power supply is, of course, unimportant!
The Op-Amp noise figure is at least five times the requested resolution! (Signal 0.1 uV, Noise 0.5 uV typical)
... ...
After that, who cares about thermal voltages, interference...
With a little more effort, a ten or twelve digits instrument is easy to implement!