According to the spec sheet only 7.5A should be necessary with a recommended 25% margin for a total 9.4A for the power supply. I rounded up to 10 for simplicity, and that's the spec of the power supply I have.
Measuring max current at peak brightness is only at ~6A though, so 10A isn't strictly necessary.
IP rating isn't necessary, it should all fit into a small box with some circuitry for PWM signaling used inside a normal room.
I haven't noticed any difference in brightness between the first and last LED. Since the power is sent via PWM controlled mosfets, splitting the power wouldn't work all that well since it inevitably have to connect the box (with the connectors) with the PWM circuitry.