How to measure the current delivered to the load by a high voltage (>50 V) non-inverting op amp amplifier?
Since you want very high resolution (and, presumably, accuracy), I don't believe any simple op amp will do the trick. Nor, for that matter, will any conventional current sensor IC. You are looking for 10 uA out of 200 mA, or .005%. Alternatively, this is a bit less than 15 bits resolution.

I suggest a rather different approach. Use a sense resistor as you have shown, but use a floated power supply to provide for a 2 MHz, 16-bit A/D converter. Use a high-speed optocoupler to transmit serial data from the ADC, along with a clock and sync channel (so you'll need 3 total). Run the A/D in continuous mode. Use the optocoupler outputs to reconstruct the current.

Go to Mouser and search the optocoupler section by speed, and you'll find a number of 50 MHz optocouplers. Since a 2 MHz sample rate will provide 2 x 16 MHz, or 32 MHz, these optos should do the job just fine.

Make sure you use power supplies rated for 100 volts of isolation.