I cant read that schematic but it looks way more complicated then it needs to be. The MAX4372 from Maxim-IC requires basically no additional circuitry and will allow you to use a resistor or more properly a shunt of very low resistance.
normally what one would do if they wanted upto 10A is use a 10 miliohm resistor and then put a 50v/v amplifier on that.
There is a nice table on page 7
http://datasheets.maxim-ic.com/en/ds...2-MAX4372T.pdf