what does reactive power mean here?
I am not seeing any reactive power there, that would require and inductor or capacitor.

During the 1 second the switch is closed current is 3V/1 ohm = 3A, and power is 9W giving a total energy expended of 9W * 1s = 9 joules, the rest of the time there is no power dissipated, so the average is indeed 1.8W integrated over 5 seconds, but I do not see where you get ~4VA from?

RMS current is (4 * 0^2 + 1 * 3^2)/5 = 1.34V, and because of the 1 ohm resistor RMS current must be 1.34A. 
1.34V * 1.34A  = 1.8W * 5s = 9 joules.