What you have looks perfectly reasonable. the sensing is... ok but the LM358 isn't a rail to rail device so you loose some range... Possibly. I'd build the current sensor and model it carefully at the rated load and then some, I'd also try it with long wires too first with a dc supply for performance and sensitivity and then go to the switcher and see that it was as stable with the switcher in place.
the issue here is to get the current sensor working first and feeding the correct information back to the Proc.. so the proc can control it
I would also give some thought to the Hall effect current sensors made by Allegro (ACH712) as they will produce a voltage that can be above Vcc/2 or below it at up to 185mV/amp, are inexpensive and don't require a sense resistor. All in all they are at first glance an ideal solution and work off of 5 volts too. I took the liberty of attaching a data sheet.
Bob
ACS712-Datasheet.pdf (652 KB)