I might be wrong but the way I think of it is that the ESC is a bridge between the battery and the motor. The motor is the power drawing element so as long as the motor amperage + 10% never exceeds the ESC rating, then in theory you should be OK.

Any idea where to get the Atmel flashing tool? I dont want to go through the hassle of soldering wires on again, but it looks like HobbyKing are out of stock of this.
I can find the USB tool quite easily: https://www.ebay.co.uk/itm/201234598699 but the atmel/atmega socket flashing adapter (the one you press the pins against the chip with) I cannot find at the moment.