One thing you can try is placing a Faraday screen between the wire and the CT. Just pass the wire through a short length of metal tubing where it goes through the hole in the CT, and ground this metal tube.
The way its scaled, 10A will produce 45mV across your 0.45 ohm resistor, and the amplifier amplifies that to 250mV.
The voltages are all fairly low which may make it more susceptible to noise.
Another way to do it might be to make R1 10 ohms, that will give you 1v for 10 amps across R1.
Then give the amplifier a gain if 0.25 by making R3 56K and R8 14K.
You could also try placing a capacitor across R8 to roll off the high frequency gain.