Oh, I know what the deal is with the 1000Amp AC current scale. There is an accessory amprobe that you plug into the meter that allows this measurement. It clamps around one of the conductors of the AC power and measures current via inductance.

Precision, high power, low resistance resistors are readily available at Electronic component supply houses. Use 1 ohm so that there is no math calculation needed. If the circuit being driven is very low resistance (or impedance) use a .1 Ohm resistor.

Have a great day,