I have 3 of these controllers and they work just dandy at 100V 40-80A. Lyen did the high voltage regen mod for me, I got the 3 position switch from him, and I have never had any single issue with any of the controllers. I was briefly running slightly over 9KW until I determined my GM isnt much faster at that power level. The controller barely was warm, generally. The only time I was concerned, was when I was towing a car down the block. The high sustained power, and very low speed, lead to a warm controller.
The Rshunt isn't an exact science, setting it to the exact number for one will only get you fairly close, not dead on. If you really care about accurite values, get something like a Watts-Up or Turnigy meter, and calibrate it yourself. Set the CA to a rough value, like 2.4 or 2.0 mOhm, it wont matter much. Go a few miles, and compare the total AH consumed, mulptily the CA shunt value by the difference between the two values, BAM, it should be as accurite as the meter you used. The resistance of the in line power analyzer will not impact the shunt value, as both should be reading identical current. The Turnigy meter is probably a better bet, due to higher current ratings, backlight, the lower price, and POT's to calibrate it yourself.
I don't see how the seller should be responsable in ANY way for informing you of the exact Rshunt value.